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Turkish Maj. Gen. flees to Russia to avoid arrest
November 18, 2011 - 21:25 AMT
PanARMENIAN.Net - Istanbul court issued an arrest warrant in August as part of a probe regarding the establishment of several websites that allegedly ran propaganda campaigns against civilian groups
Maj. Gen. Mustafa Bakici, for whom an Istanbul court issued an arrest warrant in August as part of a probe regarding the establishment of several websites that allegedly ran propaganda campaigns against civilian groups on behalf of the Turkish Armed Forces (TSK), has fled to Russia to evade arrest, Turkish media reported on Friday, Nov 18.
Bakici, who was the commander of the 23rd Border Division Command, was assigned to a desk job at the Land Forces Command's inspection department during this year's Supreme Military Council (YAS) due to his suspected involvement in the anti-government website campaign. He was among the 14 suspects for whom the Istanbul 13th High Criminal Court issued arrest warrants as part of the investigation on Aug. 8 after an indictment prepared by the prosecutor overseeing the case was accepted by the court.
After an appeal he filed against the arrest warrant was rejected, he was hospitalized at the Gulhane Military Academy of Medicine (GATA) shortly after the arrest warrant was issued and had recently been released from GATA. He began his new position at the Land Forces Command but submitted a petition for one month of leave that was approved by his superiors. The general's whereabouts have been unknown since then.
Bakici, who refused to turn himself in to prosecutors, reportedly submitted a petition to the Land Forces Command via his wife and requested retirement. Although the General Staff's legal department opposed his retirement on the grounds that the general should have been handed over to civilian prosecutors and that approving his retirement would be illegal, his petition for retirement was approved in the end and he retired on Sept. 20.
After Bakici's family said they didn't know where he was, police informed border gates and airports of the situation and discovered that Bakici had left the country and fled to Russia through northern Iraq. He was also discovered to have withdrawn all the money from his bank accounts, which some reports say amounted to TL 300,000, before his escape.
Bakici is among the key suspects in the ongoing investigation into the alleged anti-government websites. The investigation into the propaganda websites began in 2010 based on evidence found in the home of retired Col. Hasan Ataman Yildirim, another suspect in the website case. Later, an anonymous tipster from inside the military sent an email to inform the public and the prosecutors that the General Staff had established 42 websites for the sole purpose of disseminating propaganda about the government and religious communities.
There are a total of 22 suspects in the propaganda website case who are being accused of attempting to overthrow the government and of leading and being a member of an armed terror organization. They are also accused of categorizing military officers according to their religious or political beliefs, possibly for future reference. Fourteen officers on active duty, four retired military officers and a public servant have been accused in the indictment.
The content of the websites indicates that they were used as part of the Action Plan to Fight Reactionaryism allegedly drafted by Col. Dursun Cicek. Cicek's suspected plan of action details a military plan to destroy the image of the ruling Justice and Development Party (AK Party) and the faith-based Gulen movement in the eyes of the public, play down the Ergenekon investigation and gather support for members of the military arrested as part of the investigation into Ergenekon, a clandestine organization nested within the state and bureaucracy accused of plotting to overthrow the government, Today's Zaman reported.
Magnitude 5.6 quake causes damages in Iran
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Armenia wants PACE fact-finding mission in Karabakh Armenia has submitted to PACE a proposal to send a fact-finding mission to the Lachin corridor, Ruben Rubinyan says.
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Make connections with other women hikers each week along the Shoreline. This is a hiking group for adult women: the walks are cardiovascular exercise in nature and over rough terrain. Baby strollers would not work well on these hikes.
Most hikes take place in Guilford, with some in Madison and Branford. Members receive a weekly e-mail on Wednesday evenings informing them of the hike location.
The group meets September through June, weather permitting.
Please note: During the summer break, you may still sign-up for the group; the walking facilitator will contact you at the end of August regarding the fall start-up.
Please call (203) 458-6699 to join the Walking Group.


text:
\section{Introduction} \label{sec:intro}

Dust, one of the common components in space, always interacts with ambient plasma and various radiations and can then be charged and transported. Multiple observations of the lunar horizon glow (LHG) by Surveyor 5, 6, and 7 provide the possible evidence of the electrostatic dust transport phenomenon on the lunar surface, which can be interpreted as forward scattering light from a cloud of micron-sized dust grains at heights within 1 m above the surface \citep{criswell1973horizon, rennilson1974surveyor, colwell2007lunar}. Subsequently, high altitude LHG observed by astronauts from orbit above the Moon was also reported during Apollo missions, which was consistent with a population of submicron-sized dust in the lunar exosphere with a scale height of approximately 10 km \citep{mccoy1976photometric, zook1991large}. Although, initially proposed to be caused by electrostatic transport, later analysis revealed that high altitude LHG events were far less frequent than indicated by earlier reports and probably produced by some other mechanism \citep{glenar2011reanalysis}. In addition, the possible evidence for electrostatic dust transport was discovered on airless bodies, such as ``dust ponds'' in craters on Asteroid 433 Eros \citep{robinson2001nature, colwell2005Dust}. To measure the dust flux variations, the Lunar Ejecta and Meteorites (LEAM) experiment was deployed on the Moon during the Apollo 17 mission, and lunar fines movement was detected earlier \citep{berg1976lunar}. However, the results were highly controversial\citep{o2011review, laursen2011apollo}. Although the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission orbited the Moon from October 2013 to April 2014, found no electrostatically lifted dust grains in the altitude range of 3-250 km above the lunar surface \citep{szalay2015search, horanyi2015permanent}, the latest finding of five dust enhancement events during the LADEE mission again provide evidence of electrostatic dust lifting from the lunar surface \citep{xie2020lunar}. Moreover, according to distinct reflectance features of lunar rocks and regolith observed by the Chang'E-3 mission launched on 2 December 2013, long-term dust activity below approximately 28 cm above the lunar surface has been identified \citep{yan2019weak}. These results provides strong evidence for the electrostatic migration of lunar dust in the vicinity of the lunar surface.

Dust grains and the lunar surface are charged mainly due to solar UV radiation and solar wind plasma \citep{horanyi1996charged, stubbs2014dependence}. The stable surface potential on a dust grain or the lunar surface could be determined according to the balance between various currents, such as the currents from solar wind electrons, solar wind protons, secondary electrons, and photoelectrons. In particular, the interaction between electrons and dust grains is complex but interesting. Dust particles can charge negatively due to electron attachment or positively as a result of secondary electron emission (SEE). This means that, in a given environment, two identical grains may have different amounts of charges or even opposite charges \citep{vaverka2013numerical}, or one particle can have opposite charges on different parts of its surface because of its rather low conductivity. Thus, dust grains can be charged to multivalued potentials corresponding to different charging conditions and/or histories \citep{meyer1982flip}. For example, the lunar surface potential changes when the Moon travels through the terrestrial bow shock. The lunar surface potential obtained in the upstream foreshock region is different from that obtained in the downstream magnetosheath region due to different environmental conditions \citep{collier2011lunar}. For electrical insulators, such as most lunar surface substances, no accurate theory can be used in astronomical applications due to the mobility and unknown lifetimes of existing charges \citep{dukes2013secondary}.

As one of the main charging mechanisms of lunar surface, the interaction between electrons and dust grains is closely related to the surface potential distribution and the dust transport characteristics. This interaction plays a prominent role on the whole surface of the Moon. A series of experiments have demonstrated the transport of dust particles exposed to electron beams, but the energies of incident electrons were below 120 eV \citep{wang2010investigation, wang2011dust, wang2016dust}. Dust particles cannot be liberated by the plasma sheath electric field alone but can lift off the surface when exposed to an electron beam with or without a background plasma \citep{wang2016dust}, which indicates the importance of electrons in dust motion. Based on these laboratory results, a new ``patched charge model'' has been proposed to explain that in typical plasma conditions, the net electrostatic force according to the shared model is not enough to overcome gravity \citep{wang2016dust}. Then, when exposed to a 120-eV electron beam, the lifting rate of dust grains over time \citep{hood2018laboratory} and the initial launch velocities of these dust grains \citep{carroll2020laboratory} have been discussed. The results show that such intense electrostatic dust lifting can only last over a short duration and that the launch velocity of electrostatically lifted dust is related to its particle size and shape. A recent laboratory investigation on silica dust lifting has been performed under an electron beam with 450 eV energy to identify the importance of the various properties, such as the packing density of the dust samples and the horizontal electric field \citep{orger2019experimental}, and the launch angle distribution of lifted dust particles \citep{orger2021experimental}.

Besides these laboratory studies, the in situ Charged Particle Lunar Environment Experiment (CPLEE) during the Apollo 14 mission has measured the fluxes of charged particles with energies ranging from 50 eV to 50 keV. The results show that the electron spectrum of 40--100 eV dominates in the low energy range on the sunlit surface in the geomagnetic tail, but a double peak spectrum has been found in the higher energy ranges, including one peak in the range of 300-500 eV and another at 5-6 keV \citep{o1970preliminary}. Subsequently, in situ missions, the Lunar Prospector (LP) and the Acceleration Reconnection Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission, has measured the electron density and temperature, electrostatic potential, and magnetic field. The results show that the electron beam has an energy up to several kiloelectron volts \citep{halekas2005electrons, halekas2009lunarp, halekas2011first, halekas2011new, halekas2014effects}. However, these missions orbited the Moon and made measurements in the lunar orbit at a high altitude, except CPLEE.

In this study, we focus on the charging and transport characteristics of anorthite particles exposed to beam electrons with an energy of 350 eV. Only incident electrons with an energy of 350 eV were considered here since during the Moon's passage through the terrestrial magnetosphere, where the Moon spends approximately 20\% of its orbit, the increased electron flux density at an energy of 300 to 500 eV has been observed by CPLEE \citep{o1970preliminary}, which means that one of the main plasma components in the magnetosphere is in the equivalent energy range. Moreover, the lunar dust sample is expected to possess the maximum secondary electron yield in the variable energy range of 300--400 eV \citep{anderegg1972secondary, willis1973photoemission, dukes2013secondary}. Here, we directly measure grain diameters and velocities with laser Doppler measurement systems and then calculate the surface potential, the electric field intensity, and the rising heights, aiming at applying the results to the research on dust charging and transport on the lunar surface, especially when the Moon is in the Earth's magnetotail. In addition, the 350-eV electron beam creates a secondary electron sheath if the surface turns out to be positively charged, which could manifest similar properties to a photoelectron sheath on the Moon. Therefore, the results could also be used in analyzing the dust activity over most of the dayside of the Moon, as well as the sloped terrain near the terminator, such as explaining the Surveyor observations of LHG.

\section{Experimental Technique}

The Lunar (Planetary) Dust Environment Simulation Platform has been developed since 2013 to measure the diameters and velocities of dust particles lifted in the simulated lunar surface environment, as shown in Figure \ref{fig:instru}. This platform mainly consists of a vacuum system, electron beam system, diameter--velocity (D--V) test system, and data collection system. In the electron beam system, an FS40A-PS Power Supply Unit, which is both a full-option control and a power supply, is employed to control the electron emission. The main operational menu allows the adjustment of characteristic parameters, for example, electron energy in the range of 0--500 eV by steps of 0.1 eV and emission current in the range of 1--500 $\rm{\mu A}$. The electron beam is produced by direct emission from a tungsten cathode ray tube.

\begin{figure*}
\gridline{\fig{instru.jpg}{0.64\textwidth}{}
          \fig{1.jpg}{0.34\textwidth}{}}
\caption{Lunar (Planetary) Dust Environment Simulation Platform: (a) Pictorial view of the experimental apparatus; (b) Image of dust transport. The measured point is at the intersection of two laser beams.
\label{fig:instru}}
\end{figure*}

In the D--V test system, a phase Doppler particle analyzer/laser Doppler velocimeter (PDPA/LDV) system from TSI (TSI Incorporated, Saint Paul, MN 55126, USA) is used (https://www.tsi.com/products/fluid-mechanics-systems/). Based on the scattering of light by a moving particle, the LDV system can measure the particle velocity. The intersection of two laser beams creates a series of light and dark fringes. The moving particle scatters light when crossing the bright fringe but scatters no light when passing the dark fringe, which results in a fluctuating pattern of scattered light intensity with a frequency ($f_{\rm{D}}$). The velocities of moving particles ($V$) can be calculated by multiplying the frequency by the known fringe spacing ($\delta_{\rm{f}}$):
\begin{equation}
V=\delta_{\rm{f}} \cdot f_{\rm{D}},
\label{eq:v}
\end{equation}
where $\delta_{\rm{f}}$ is determined by the laser wavelength ($\lambda$) and the angle ($2\kappa$) between beams:
\begin{equation}
{\delta _{\rm{f}}}{\rm{ = }}\frac{\lambda }{{2\sin \left( \kappa  \right)}}.
\label{eq:deltaf}
\end{equation}
Note that the frequency of one laser beam was shifted by a Bragg cell by 40 MHz to judge the velocity direction and even to measure velocities near zero. Laser beams are supplied by the PowerSight Laser Velocimeter system with an external beam steering module, which allows the steering of laser beams.

The particle diameter ($D$) can be obtained by the phase Doppler technique, which is an extension of LDV, allowing the size measurements of spherical particles, including liquid sprays as well as some bubbles and solid spheres, to be obtained. The spatial frequency (spacing between the scattered fringes at the light collecting optics) of the scattered fringes can be measured as a phase shift ($\Phi$) between two electrical signals resulting from the scattered light. The diameter is correlated to the phase shift between two laser beams from two corresponding detectors at different positions:
\begin{equation}
D{\rm{ = }}\frac{{L_{\rm{f}}{\delta_{\rm{f}}}\Phi }}{{2\pi \Delta l}}K,
\label{eq:D}
\end{equation}
where $K$ is the optical constant, $ \Delta l$ is the space between two detectors, and $L_{\rm{f}}$ is the lens focal length. In addition, data acquisition and processing were achieved by commercial FLOWSIZER 64 software.

As shown in Figure \ref{fig:setup}, the laser source, the PDPA/LDV detector, and the sample stage are deployed in the same horizontal plane, while the filament, the PDPA/LDV detector, and the sample stage are in the same vertical plane. Note that an insulating plate is placed between the sample box and the sample stage. The sample stage and the vacuum chamber are grounded. A voltmeter that directly connects the sample box and the ground is employed to build a real-time measure of the voltage on the sample box. The measured point of dust transport was at the intersection of two laser beams, and the height ($h_0$), namely, the distance between the measured point and the sample surface, can be adjusted by moving the sample stage in the vertical direction. In this experiment, $h_0$ was set to be 6 mm.

\begin{figure}
\epsscale{0.8}
\plotone{setup.jpg}
\caption{Experimental setup. The LDV system allows anorthite particles with velocity in the range of $-$90 to 283 $\rm{m~s^{-1}}$ to be detected; the PDPA system measures the particles with diameter in the range of 0.5 to 90 $\rm{\mu m}$.
\label{fig:setup}}
\end{figure}

In our study, by using the laser Doppler method, the size and velocity of anorthite particles ejected from a dusty surface can be better characterized than previous studies. The particle size and the vertical velocity were measured simultaneously. The velocity in the range of $-$90 to 283 $\rm{m~s^{-1}}$ with measurement accuracy of 0.2\% can be measured, including the vertical velocity ($V_{\rm{z}}$) and the horizontal velocity ($V_{\rm{x}}$) of the moving particles. The measurable particle size is in the range of 0.5 to 90 $\rm{\mu m}$ with measurement accuracy of 0.5\%. In previous studies, as shown in Table \ref{tab:comp}, the dust transport process was recorded by a high-speed video camera, and dust velocities and diameters were extracted from stacked images \citep{wang2016dust, hood2018laboratory, orger2019experimental, carroll2020laboratory}. However, partial dust migration cannot be detected or tracked by cameras, such as grains whose diameters were lower than several microns (limited by the image resolution), grains that cannot reflect sufficient light consistently, and grains that travel away from the focus range of the camera \citep{orger2019experimental}. For example, the smallest dust particles resolved in Carroll's experiments was approximately 11 $\rm{\mu m}$, and the dust velocities were theoretically calculated, based on the patched charge model and the energy conservation law. Modeling dust migration precisely is difficult because of the randomness of the charging and transport processes of isolated particles. Here, we focus on the group migration behavior of smaller dust grains (0.5--40 $\rm{\mu m}$) based on the statistical particle size and velocity. These particles were similar in size to those putatively observed to have been electrostatically transported on the Moon, e.g., the diameters of dust particle inferred from LHG observed by Surveyor lander TV cameras were approximately 10 $\rm{\mu m}$. Smaller anorthite particles have similar pore sizes and cohesive forces between grains with the lunar regolith. The pore sizes are important for charging mechanisms at the surface, especially for the patched charging model. Second, smaller particles tend to have stronger cohesive forces than larger particles. This means that the results of the experiments are more directly relevant to dust electrostatically transported in the lunar environment. Moreover, a higher electron emission current was used in our experiments to lift more dust grains.

\begin{deluxetable*}{cccc}
\tablenum{1}
\tablecaption{Comparison of experimental methods and conditions between previous works and this experiment\label{tab:comp}}
\tablewidth{0pt}
\tablehead{
\colhead{Research} & \colhead{experimental methods } & \colhead{Diameter range} & \colhead{Electron energy}
}
\startdata
\citet{wang2016dust}, \citet{carroll2020laboratory} & high-speed video camera & 7-140 $\rm{\mu m}$ & 120 eV \\
\citet{orger2019experimental} & high-speed video camera & 2.4--19$\rm{\mu m}$/pixel & 450 eV \\
This experiment & PDPA/LDV system & 0.5-90 $\rm{\mu m}$ & 350 eV \\
\enddata
\tablecomments{The diameter range represents the range of particle size that can be detected by the corresponding method, rather than the range of particle size measured in the research. }
\end{deluxetable*}

\section{Dust Transport Measurements}

\subsection{Experimental Setup}

Anorthite is one of the major minerals in lunar dust, featuring excellent insulation and a high work function ($\sim$5.58 eV) \citep{li2016indication}. It can acquire charges and even maintain them for a long period. Meanwhile, compared with other lunar surface materials, it may transport easily due to the lower mass density. Therefore, anorthite particles are being treated as a proxy for lunar regolith here. We assume that anorthite particles share similar relevant characteristics to lunar dust, such as shape, secondary emission yields, secondary electron temperatures, etc. In our experiments, anorthite grains were obtained from gabbro (the original rock) in Xigaze, China. The gabbro was crushed preliminarily, and then magnetic substances in the samples were removed by magnetic separation to avoid their influence on the incident electrons and the electrostatic migration of anorthite particles. The collected sample used in our experiments contains $>$90 vol\% anorthite and a small amount of albite. We sieved anorthite particles further to remove particles with sizes greater than 40 $\rm{\mu m}$. Before being measured, the sample was baked at $110{\degr}$C for 24 hours in atmospheric conditions and then deaerated in the vacuum chamber with $10^{-6}$ Pa pressure for 12 hours to remove adsorbed gases.

These experiments were carried out in a hemispherical stainless-steel vacuum chamber, 50 cm in diameter, with a base pressure of approximately $10^{-6}$ Pa. The beam currents ($I_{\rm{e}}$) used in these experiments were fixed at 500 $\rm{\mu A}$ to increase the moving anorthite grain flux. To avoid the effect of a large electric field at the boundary of the beam-illuminated region and the shadow region, as researched by \citet{wang2011dust}, the beam spot size was tuned to 10 mm (the sample box was 8 mm$\times$8 mm). Thus, the beam electron flux ($J_{\rm{e}}$) was approximately 6.4 $\rm{A~{m^{-2}}}$, based on ${J_{\rm{e}}=I_{\rm{e}}/{s}}$, where $s$ is the electron beam spot area. The available incident electron energy was 0--500 eV. However, we found that no significant dust movement was detected under beam electrons below 150 eV, probably because the electric field at the primary electron energy of approximately 150 eV could not push much dust off the surface. From 200 to 500 eV, the response time required for the first dust to leave from the surface gradually decreased but did not significantly change when the incoming electron energy was higher than 300 eV. Here, the measurements under the electron beam with an energy of 350 eV were eventually discussed. The height of the measured point here was 6 mm above the sample surface.

\subsection{Diameter and Velocity}

Ten experiments were carried out to measure the diameters and velocities of the moving anorthite particles. Each experiment lasted 5--25 minutes. In all of these experiments, 1125 diameter signals were detected, but there were 20 particles with diameters between 20 and 40 $\rm{\mu m}$ and only 11 particles larger than 40 $\rm{\mu m}$, probably due to particle aggregation. Figure \ref{fig:dvv}(a) shows the diameter distribution. The counts of diameter signals decrease with increasing particle size, and 79.11\% of lifted anorthite particles were smaller than 5 $\rm{\mu m}$.

\begin{figure*}
\gridline{\fig{D1_20um_line.jpg}{0.5\textwidth}{(a)}}
\gridline{\fig{V1_1.jpg}{0.5\textwidth}{(b)}}
\gridline{\fig{V2_1.jpg}{0.5\textwidth}{(c)}}
\caption{Distributions of the (a) diameter, (b) vertical velocity, and (c) horizontal velocity of lifted anorthite particles under the electron beam with an energy of 350 eV. Gaussian distribution curves of $V_{\rm{z}}$ and $V_{\rm{x}}$ are given by the red lines in (b) and (c).
\label{fig:dvv}}
\end{figure*}

Both vertical velocities ($V_{\rm{z}}$) and horizontal velocities ($V_{\rm{x}}$) of the moving particles were measured in these experiments. We recorded 2961 vertical velocity signals and 859 horizontal velocity signals, as shown in Figures \ref{fig:dvv}(b) and (c), respectively. $V_{\rm{z}}$ ranges from $-$9.74 to 7.10 $\rm{m~s^{-1}}$, but 91.46\% of them are in the range of $-$2 to 2 $\rm{m~s^{-1}}$. $V_{\rm{x}}$ falls between $-$5.38 and 3.38 $\rm{m~s^{-1}}$, and particles with speeds below 1 $\rm{m~s^{-1}}$ occupy 88.48\%. Gaussian distribution curves of $V_{\rm{z}}$ and $V_{\rm{x}}$ show that there is no significant difference between lifted and falling particles or for particles moving along orthogonal horizontal directions. This indicates that the velocities of anorthite particles are influenced only by gravity and electrostatic forces, and only a miniscule number of particles can reach the chamber ceiling. In other words, the maximum heights of most particles did not exceed 25 cm.

We detected many more signals of the vertical velocity than of the diameter because only one detector is needed to measure velocities, while two detectors are required to obtain particle diameters. Thus, a velocity can be obtained, but the corresponding diameter cannot be obtained if only one detector obtains the signal. On the other hand, the signals of anorthite particle diameters that were below the detection limit of the diameter signal cannot be detected. Furthermore, the number of $V_{\rm{z}}$ signals is greater than that of $V_{\rm{x}}$ signals by a factor of approximately 3.5, since part of the horizontal velocity signals, for example those perpendicular to the $V_{\rm{x}}$ and $V_{\rm{z}}$ directions, cannot be detected. In addition, $V_{\rm{z}}$ falls in a wider range than $V_{\rm{x}}$, though for these particles, gravity needs to be overcome in the vertical direction. The results reveal the dominance of the vertical migration of anorthite particles. The horizontal velocities are mainly ascribed to the effect of the sample box and other nearby grains on the local electric field.

\subsection{Transport Rate of Anorthite Particles}

To characterize anorthite particle migration, we calculate the average transport rates of lifting particles at the measured point. Counts of cumulative lifted particles are calculated by counting the $V_{\rm{z}}$ signal. Overall, the average rates are mainly limited in the range of 0.1--1.7 particles per second at the measured point. As shown in Figure \ref{fig:rate}, the transport rates decreased with time/depth. Dust activity could be detected with depth, but stronger charging was required to detach the particles due to the increasing packing density and the increasing contact surfaces between the dust grains \citep{orger2019experimental}. This phenomenon is consistent with early experimental results that a lifting rate peaks at the beginning and then slows down \citep{hood2018laboratory}.

\begin{figure}
\epsscale{0.65}
\plotone{rate.jpg}
\caption{Transport Rates of anorthite particles from ten experiments.
\label{fig:rate}}
\end{figure}

Note that this is a type of experiment with sample loss. Anorthite particles in the sample box were reduced since some lifted particles hit the vacuum chamber ceiling and stuck to it, and some lifted particles traveled away from the sample box due to horizontal transport. Anorthite particles in the sample box can be removed completely in a few hours because the thickness of the dust sample is less than 1 mm, so each experiment was set to last from a few minutes to less than thirty minutes.

The dust migration rates in the first few minutes of each experiment almost maintained constant. As an example, we plot the counts of cumulative lifted particles based on vertical velocities signals. Figure \ref{fig:d17}(a) shows $V_{\rm{z}}$ of lifted dust particles. As mentioned above, the number of upward anorthite particles is approximately the same as that of the downward particles. Particle velocities are mostly in the range of $-$2 and 2 $\rm{m~s^{-1}}$. The number of cumulative lifted particles increases linearly with time, as shown in Figure \ref{fig:d17}(b). The lifting rate is flat during the first 5 minutes, and the average rate is 0.83 particles per second. Interestingly, several or even more than 10 particles were detected almost synchronously. Then after a short time interval ranged from 1 to 12 s, another group of dust particles appeared. This irregular pulse migration is a new phenomenon, implying that the dust particles could be lifted in groups.

\begin{figure}
\epsscale{0.65}
\plotone{d17.jpg}
\caption{(a) The vertical velocity of dust particles as a function of measuring time. (b) The number of cumulative lifted anorthite particles as a function of time based on $V_{\rm{z}}$ signal counts. Note that the time when the first dust particle was liberated was set as the initial time.
\label{fig:d17}}
\end{figure}

\section{Discussions}

The experiments were performed below a pressure of $10^{-6}$ Pa. Based on the dynamic fountain model \citep{stubbs2006a} and the recently proposed patched charge model \citep{wang2016dust}, anorthite particles attained charges under electron beam irradiation, and then the electrostatic force ($F_{\rm{es}}$) and the particle-particle repulsive force ($F_{\rm{c}}$) acting on the grains increased. Figure \ref{fig:force} shows the evolution of forces acting on anorthite particles at different heights during dust migration. Once sufficient charges were obtained, that is, $F_{\rm{es}}$ and $F_{\rm{c}}$ became large enough to overcome the gravity ($G$) and the cohesive force ($F_{\rm{co}}$), the particles would be repelled and released by the charged surface with initial velocity ($V_0$). Then, some anorthite particles decelerate in the electrical field and return to the sample surface; and some particles accelerate or decelerate upward through the electrical field, which depends on the magnitude of $F_{\rm{es}}-G$. The particles that can leave the electrical field are decelerated by gravity outside the electrical field and reach the maximum height ($H$). Finally, following a ballistic trajectory, these particles fall back towards the surface. During these processes, the diameters and velocities of lifted anorthite particles were measured at an altitude of 6 mm.

\begin{figure}
\epsscale{0.7}
\plotone{force-1.jpg}
\caption{(a) Schematic diagram of the experiments; (b) evolution of forces acting on anorthite particles. The green dot in (b) is the measured point corresponding to the intersection of the two laser beams in (a). $h'$ represents the rising height of anorthite particles after reaching the measured point. $\lambda_{\rm{D}}<h_0$ if the sample surface was positively charged; while $d>h_0$ if the surface was negatively charged, and whether the particles could leave the electric field depended on the initial velocities of the particles and their force situation in the field. Note that in the patched charge model, the electric field force was downward if the particle was negatively charged and the sample surface was positively charged.
\label{fig:force}}
\end{figure}

The charging characteristics of anorthite particles and the sample surface determined the electrostatic force and the particle-particle repulsive force acting on anorthite particles as well as the transport characteristics of these particles. Therefore, to further understand the charging and transport characteristics of anorthite particles, we need to first analyze the electric field above the sample surface, such as the equilibrium surface potential and the electric field intensity.

\subsection{Electric Field above the Sample Surface}

In these experiments, anorthite particles were exposed to a 350-eV electron beam without the background plasma. The incident electron beam impacting dust grains is assumed to be well collimated and has initial energy ($E_0$), which can be regarded as a purely monoenergetic beam. To characterize the charging process of the sample surface, we only consider three major charging currents: primary electron current ($I_{\rm{e}}$), secondary electron current ($I_{\rm{se}}$), and backscattered electron current ($I_{\rm{be}}$). Note that the secondary and backscattered electrons from the sample box were neglected.

For an uncharged surface ($\phi_{\rm{0}}=0$), the arriving electron flux ($J_{\rm{e}}$) can be given by
\begin{equation}
{J_{\rm{e}}} = e{n_{\rm{e}}}\sqrt {\frac{{2E_0}}{{{m_{\rm{e}}}}}},
\label{eq:Je}
\end{equation}
where $e$ represents the elementary charge ($1.60\times 10^{-19}$ C). $n_{\rm{e}}$ and $m_{\rm{e}}$ are the electron density and the electron mass ($9.11\times 10^{-31}$ kg), respectively. $n_{\rm{e}}$ was approximately $3.6 \times 10^6$ $\rm{cm^{-3}}$ for the incident electron beam with an energy of 350 eV. For a charged surface with a potential ($\phi_{\rm{s}}$), when beam electrons approach the surface, the electron energy ($E_{\rm{pe}}$) changes and can be determined by $E_{\rm{pe}} = E_0 +e\phi_{\rm{s}}$. Then, the arriving electron flux ($J_{\rm{pe}}$) can be written in the following form \citep{chow1994secondary}:
\begin{equation}
{J_{\rm{pe}}} = e{n_{\rm{pe}}}\sqrt {\frac{{2(E_0 + e{\phi_{\rm{s}}})}}{{{m_{\rm{e}}}}}},
\label{eq:Jpe}
\end{equation}
where $n_{\rm{pe}}$ is the electron density before impacting the charged surface.
Since the incident electron current was fixed, ${J_{\rm{e}}}$ was equal to ${J_{\rm{pe}}}$ when the electron beam was well collimated. Here, we assume that it took a finite time to charge the bulk sample surface and that the surface had reached the equilibrium surface potential ($\phi_{\rm{s}}$) before any grains left from the surface.

The equilibrium potential could be positive or negative, depending on the yields of secondary electrons and backscattered electrons for the bulk sample surface covered by anorthite particles, $\delta(E_0)$ and $\eta(E_0)$, respectively. For $\delta(E_0)+\eta(E_0)<1$, the sample surface was charged to a negative potential, $\phi_{\rm{s}}<0$. The incoming electrons were repelled and decelerated. Electrons with energy lower than $-e\phi_{\rm{s}}$ could not reach the bulk sample surface. For $\delta(E_0)+\eta(E_0)>1$, the surface was charged to a positive potential, $\phi_{\rm{s}}>0$. The beam electrons were attracted and accelerated. All the electrons can reach the bulk sample surface. However, the excited secondary electrons with energy lower than $e\phi_{\rm{s}}$ could not escape from the range of surface potential. Here, the emitted secondary electrons are assumed to have a Maxwellian velocity distribution, and the backscattered electrons leaving the sample surface are considered to have a similar but somewhat lower energy than they had upon entering, but have an isotropic distribution due to the randomisation of their velocities \citep{whipple1981potentials}. That means the energy of backscattered electrons can be obtained by ${E_{\rm{be}}}=E_0+e\phi_{\rm{s}}$. Therefore, the escaping secondary and backscattered electron flux, namely, $J_{\rm{se}}$ and $J_{\rm{be}}$, can be obtained as follows \citep{stubbs2014dependence}:
\begin{equation}
{J_{\rm{se}}} = -e{n_{\rm{se}}}\sqrt{\frac{{{k_{\rm{B}}}{T_{\rm{se}}}}}{{2\pi{m_{\rm{e}}}}}}\exp(-{\frac {e{\phi_{\rm{s}}}}{{{k_{\rm{B}}}{T_{\rm{se}}}}}})=-\delta(E_0{\rm{ + }}e{\phi_{\rm{s}}}){J_{\rm{pe}}}\exp(-{\frac {e{\phi_{\rm{s}}}}{{{k_{\rm{B}}}{T_{\rm{se}}}}}}), \ \ \ \ (\phi_{\rm{s}}>0)
\label{eq:Jse1}
\end{equation}
\begin{equation}
{J_{\rm{se}}} = -e{n_{\rm{se}}}\sqrt{\frac{{{k_{\rm{B}}}{T_{\rm{se}}}}}{{2\pi{m_{\rm{e}}}}}}=-\delta(E_0{\rm{ + }}e{\phi_{\rm{s}}}){J_{\rm{pe}}}, \ \ \ \ (\phi_{\rm{s}}<0)
\label{eq:Jse2}
\end{equation}
\begin{equation}
{J_{\rm{be}}}=-e{n_{\rm{be}}}\sqrt {\frac{2(E_0{\rm{ + }}e{\phi_{\rm{s}}})}{{{m_{\rm{e}}}}}} =-\eta(E_0{\rm{ + }}e{\phi_{\rm{s}}}){J_{\rm{pe}}},
\label{eq:Jbe}
\end{equation}
where $k_{\rm{B}}$ is the Boltzmann constant ($1.38\times10^{-23}$ $\rm{J~K^{-1}}$). ${n_{\rm{se}}}$, ${T_{\rm{se}}}$ and $\delta(E_0{\rm{ + }}e{\phi_{\rm{s}}})$ are the density, temperature and yield of the secondary electrons escaping from the bulk sample surface covered by anorthite particles, respectively. ${n_{\rm{be}}}$ and $\eta(E_0{\rm{ + }}e{\phi_{\rm{s}}})$ are the density and yield of the emitted backscattered electrons. Note that anorthite is a near-perfect insulator so that no significant current flows through the sample surface or to the sample box.

(1) Equilibrium Surface Potential

Kirchhoff's law states that all incoming currents are equal to all outgoing currents under equilibrium conditions, which can be used to derive the equilibrium surface potential ($\phi_{\rm{s}}$). That is, the net electron flux satisfies ${J_{\rm{net}}} = 0$. Based on Equations (\ref{eq:Jpe}--\ref{eq:Jbe}), the current balance equation satisfies that:
\begin{equation}
e{n_{\rm{pe}}}\sqrt {\frac{{2(E_0 + e{\phi_{\rm{s}}})}}{{{m_{\rm{e}}}}}} \left[{1 - \delta(E_0 + e{\phi_{\rm{s}}})\exp(-{\frac {e{\phi_{\rm{s}}}}{{{k_{\rm{B}}}{T_{\rm{se}}}}}}) - \eta(E_0 + e{\phi_{\rm{s}}})}\right]= 0, \ \ \ \ (\phi_{\rm{s}}>0)
\label{eq:Jnet1}
\end{equation}
\begin{equation}
e{n_{\rm{pe}}}\sqrt {\frac{{2(E_0 + e{\phi_{\rm{s}}})}}{{{m_{\rm{e}}}}}} \left[ {1 - \delta(E_0 + e{\phi_{\rm{s}}}) - \eta(E_0 + e{\phi_{\rm{s}}})} \right] = 0.
 \ \ \ \ (\phi_{\rm{s}}<0)
\label{eq:Jnet2}
\end{equation}
It means that the current balance can be obtained by a self-consistent physical process among the surface potential ($\phi_{\rm{s}}$) and the yields of secondary electrons ($\delta(E_0 + e{\phi_{\rm{s}}})$) and backscattered electrons ($\eta(E_0 + e{\phi_{\rm{s}}})$). If $\delta(E_0 + e{\phi_{\rm{s}}}) + \eta(E_0 + e{\phi_{\rm{s}}})>1$, the insulating anorthite particles were considered to be positively charged. We assume that ${T_{\rm{se}}}=3~{\rm{eV}}$, $\delta(E_0 + e{\phi_{\rm{s}}})=1.5$ and $\eta(E_0 + e{\phi_{\rm{s}}})=0.1$ \citep{vaverka2016lunar}, thereby the bulk surface potential is $\phi_{\rm{s}}=1.5~{\rm{V}}$. It's worth noting that the different ${T_{\rm{se}}}$ values have a negligible effect on the following results. If $\delta(E_0 + e{\phi_{\rm{s}}}) + \eta(E_0 + e{\phi_{\rm{s}}})<1$ in 0-350 eV energy range, anorthite particles charged negatively. The surface potential could reach $\phi_{\rm{smax}}=-350~{\rm{V}}$. If $\delta(E_0 + e{\phi_{\rm{s}}}) + \eta(E_0 + e{\phi_{\rm{s}}})=1$ at some energy point $E_{\rm{pe}}$ in 0-350 eV energy range, then the surface potential $\phi_{\rm{s}}$ could be obtained by $(E_{\rm{pe}}-E_{\rm{0}})/e$.

(2) Electric Field Intensity

If the surface charged positively, it was shielded by backscattered electrons and secondary electrons. Therefore, the Debye length (${\lambda_{\rm{Di}}}$) related to secondary electrons or backscattered electrons can be expressed as
\begin{equation}
{\lambda _{\rm{Di}}}{\rm{ = }}\sqrt {\frac{{{\varepsilon _0}{k_{\rm{B}}}{T_{\rm{i}}}}}{{{e^2}{n_{\rm{i}}}}}} ,
\label{eq:lambda0}
\end{equation}
where $\varepsilon _0$ is the permittivity of free space ($8.85\times10^{-12}$ $\rm{F~m^{-1}}$). Note that the subscript $i$ represents $be$ when backscattered electrons dominate in the shielding process, or $se$ when secondary electrons dominate. Based on Equation (\ref{eq:Je}--\ref{eq:Jbe}), $n_{\rm{se}}$ and $n_{\rm{be}}$ can be written as follows:
\begin{equation}
n_{\rm{se}}=\delta(E_0+e\phi_{\rm{s}}) n_{\rm{e}}\sqrt{\frac{4\pi{E_0}}{{{{k_{\rm{B}}}{T_{\rm{se}}}}}}},
\label{eq:nse}
\end{equation}
\begin{equation}
n_{\rm{be}}=\eta(E_0+e\phi_{\rm{s}}) n_{\rm{e}}\sqrt {\frac{E_0}{E_0 + e{\phi_{\rm{s}}}}}.
\label{eq:nbe}
\end{equation}
In Equation (\ref{eq:nbe}), the effect of a positive surface potential on the backscattered electron flux was considered negligible, since the energy of backscattered electrons satisfied $E_{\rm{be}}\gg e{\phi_{\rm{s}}}$ when the surface was positively charged, such that they would all escape from a small positive surface potential. With the above assumed emission parameters for secondary and backscattered electrons, we obtain ${\lambda_{\rm{Dse}}=0.9}$ mm and ${\lambda_{\rm{Dbe}}=232.3}$ mm. Since the Debye length is determined by $1/{\lambda_{\rm{D}}^2}=1/{\lambda_{\rm{Dse}}^2}+1/{\lambda_{\rm{Dbe}}^2}=$0.9 mm, this means that the secondary electrons dominate shielding process, while backscattered electrons have a negligible effect on shielding. In this case, the vertical electric field intensity ($E$) was estimated by ${\phi_{\rm{s}}}/{\lambda_{\rm{D}}}=1.7\times$10$^{3}$ $V~m^{-1}$. Note that the Debye sheath is lower than the monitoring position, namely, ${\lambda_{\rm{D}}}<{h_0}$.

If the surface charged negatively, there is no Debye shielding effect. The electric field could extend to a much larger effective distance $d$, its intensity can be approximately estimated by $E=\phi_{\rm{s}}/d$. Since the size of sample box is 8 mm$\times$8 mm, the effective distance $d$ should be larger than $h_{0}$ of 6 mm, namely $d>h_{0}$.

\subsection{Secondary Electron Emission Characteristics}

Exposed to beam electrons with an energy of 350 eV, the magnitude and polarity of the surface potential of bulk anorthite particles depend on the secondary electron yield. For the individual grains, the maximum secondary electron yield ($\delta_{\rm{M}}$) is approximately 3.2 at the peak energy of $E_{\rm{M}}=350$ eV, based on experimental results on Apollo 11 and 17 dust samples, Minnesota Lunar Simulant (MLS-1), Johnson Space Center (JSC-1) lunar simulant and Lunar Highlands Type (LHT) regolith simulant \citep{horanyi1998electrostatic, nemecek2011lunar}. However, for the bulk dust surface, the maximum yield of 1.4--1.6 has been obtained at approximately 350 eV excitation energy for Apollo 14 and 15 samples \citep{anderegg1972secondary, willis1973photoemission}, while for the Apollo 16 sample, the maximum yield of 1.13 has also been measured at incident energies below 200 eV \citep{dukes2013secondary}. Lunar Prospector (LP) in-situ measurements also show that the secondary electron yield of lunar regolith is lower than the single-particle laboratory results by a factor of 2--3 \citep{halekas2009lunars}.

The yield reduction is attributable to the scattering and absorption of secondary electrons within microcavities between dust particles, which markedly reduces the escape probability of secondary electrons \citep{anderegg1972secondary, bruining1954physics} and further influences the current balance at the lunar surface and the resulting equilibrium surface potentials \citep{halekas2009lunars}.

\citet{vaverka2016lunar} have discussed the effect of the reduction factors of 2--4 for both the secondary and backscattered electron yields on the lunar surface potentials. The results show that the surface potential oscillates from slightly positive to negative up to $-$50 V for a reduction factor of 2, and higher factors lead to higher negative potentials. In our experiment, the real reduction factor could be related to the stacking structure of anorthite particles. But according to previous experiments, in-situ LP measurements, and the theoretical calculation, the reduction factor of approximately 2--4 for the secondary electron yield of anorthite particles is taken into consideration in our analysis.

In addition, the backscattered electron yield of a single dust particle increases with the atomic number and the material density, but it always falls between 0.2 and 0.3 for incident electrons with energies of several hundred electron volts. If the reduction factor for the bulk anorthite particles is about 2, taking a typical value of $\delta(E+e\phi_{\rm{s}})=1.5$ and $\eta(E+e\phi_{\rm{s}})=0.1$, a surface equilibrium potential of 1.5 V is obtained according to Equation (\ref{eq:Jnet1}). In our experimental setup, no surface potential measurement is available. We cannot exclude the possibility of a higher reduction factor. For example, if the reduction factor is 4, that is, $\delta(E_0 + e{\phi_{\rm{s}}}) + \eta(E_0 + e{\phi_{\rm{s}}})<1$, the surface could be negatively charged with a maximum negative potential of $-350~{\rm{V}}$. If $\delta(E_0 + e{\phi_{\rm{s}}}) + \eta(E_0 + e{\phi_{\rm{s}}})=1$ at some energy point $E_{\rm{pe}}$, then the surface potential $\phi_{\rm{s}}$ could be obtained by $(E_{\rm{pe}}-E_{\rm{0}})/e$. These results are consistent with the previous calculation that the potential in the magnetosphere could vary from approximately $-$200 V to $+$10 V depending on the SEE yield of the surface \citep{vaverka2016lunar}. Based on Vaverka's calculation, regardless of secondary electron emission, the potentials can reach approximately $-$400 V. Actually, the lunar surface is also observed to charge negatively \citep{halekas2008lunar, halekas2011first, saito2014night}. More in-situ measurements of the near-surface electric field distribution are needed when the Moon is in the terrestrial magnetotail to study the diversity of charging properties at different places. We will also consider to measure the surface potential and the electric field intensity directly in the subsequent experiments.

\subsection{Dust Transport Dynamics}

(1) Dust Transport Dynamics

Under the irradiation of beam electrons, the electrostatic force and the particle-particle repulsive force are the main driving force for the anorthite particle migration. In the shared charge model \citep{flanagan2006dust}, a uniform charge distribution over the surface of each dust particle is assumed, and the charge of each dust particle with radius ${r_{\rm{d}}}$ is given by
\begin{equation}
q_{\rm{s}}=4\pi{\varepsilon _0}{r_{\rm{d}}}^2E.
\label{eq:qmin}
\end{equation}
If the electric force $q_{\rm{s}}E$ could overcome the gravity and cohesive force, the dust could be lifted.

In the isolated capacitors model \citep{flanagan2006dust, stubbs2006a}, the dust particle is assumed to be charged as if it were an isolated sphere immersed in a plasma, while the effects of the nearby surface is neglected. As a result, the dust charge is given by
\begin{equation}
q_{\rm{ic}}=4\pi{\varepsilon _0}{r_{\rm{d}}}\phi_{\rm{s}}.
\label{eq:qmax}
\end{equation}
In the patched charge model \citep{wang2016dust}, the emission and re-absorption of photoelectrons and/or secondary electrons at the walls of microcavities formed between neighboring dust particles below the surface could produce large unexpectedly negative charges, the dust charge is given by
\begin{equation}
q_{\rm{p}}=-2\pi{\varepsilon_0}r_{\rm{d}}(\frac{\xi T_{\rm{se}}} {e})=-4\pi{\varepsilon_0}r_{\rm{d}}\phi_{\rm{p}}.
\label{eq:qpartch}
\end{equation}
Here, $\xi$ is an empirical constant between 4 and 10 based on measurements \citep{wang2016dust}. $\phi_{\rm{p}}=\frac{\xi T_{\rm{se}}}{2e}$ could be regarded as an effective charging potential. The charge of dust particles could be enhanced by several orders of magnitudes compared to shared charge model for micron-sized particles. The lift of dust particles are mainly caused by the intense particle-particle repulsive forces $F_{\rm{c}}$ near the surface, which result in a substantial initial emission velocity $V_{0}$ of the dust particle. The dust's initial velocity $V_{0}$ plays an important role in the upward dust transportation.

In the shared charge model and isolated capacitors model, the electric field force $F_{\rm{es}} = Eq$ is the main driving force. To lift the dust particles, $F_{\rm{es}}$ should be larger than the gravity and cohesive force. The gravity can be obtained by $G={\frac{4}{3}}{\rho}\pi{r_{\rm{d}}}^3g$, where $\rho$ is the density of anorthite particles (2.61 ${\rm{g~cm^{-3}}}$) and $g$ is the gravitational acceleration. Assuming a zero cohesive force and taking $q=q_{\rm{ic}}$, one can calculate the maximum diameter $D_{\rm{max}}$ of anorthite grains which could be lifted. If the surface was positively charged with a potential of 1.5 V, $D_{\rm{max}}$ is 3.3 $\rm{\mu m}$, far below the diameter of the released dust observed in our experiment. Since $q_{\rm{ic}}$ is much larger than  $q_{\rm{s}}$, $D_{\rm{max}}$ could be much smaller than 3.3 $\rm{\mu m}$ according to the shared charge model, which is inconsistent with our diameter measurements. For a negatively charged surface, the surface potential could reach $-$350 V at most. Assuming $q=q_{\rm{ic}}$, $D_{\rm{max}}$ could be larger than 100 $\rm{\mu m}$. Actually, the maximum particle diameter observed in the experiments was also larger than 100 $\rm{\mu m}$.

During the dust transport process, only the gravity and the electrostatic force worked in the shared charge model and the isolated capacitors model. Based on the energy conservation law, the vertical velocity (${V_{\rm{z}}}$) and the diameter ($D$) satisfy the following relationships:
\begin{equation}
\frac{1}{2}m{V_{\rm{0}}}^2= \frac{1}{2}m{V_{\rm{z}}}^2+mgh_0-Eqh_{\rm{E}},
\label{eq:energ}
\end{equation}
where $h_{\rm{E}}$ is the effective acting range of the electric field. $h_{\rm{E}}={\lambda_{\rm{D}}}$ for the positively charged surface. For the negatively charged surface, we consider that the upper boundary of the electric field is higher than the measured point, according to the discussion in Section 4.1, namely $d>h_0$. That is, $h_{\rm{E}}={h_{\rm{0}}}$ for the negatively charged surface.

To characterize the relationship between the diameter $D=2{r_{\rm{d}}}$ and the vertical velocity at $h_{0}$, based on Equations (\ref{eq:qmin}-\ref{eq:qmax}) and $m={\frac{4}{3}}{\rho}\pi{r_{\rm{d}}}^3$, Equation (\ref{eq:energ}) can be written as:
\begin{equation}
{V_{\rm{z}}}^2=A{D^{-2}}+C,\ \ \ \ (q=q_{\rm{ic}})
\label{eq:vd1}
\end{equation}
\begin{equation}
{V_{\rm{z}}}^2=B{D^{-1}}+C,\ \ \ \ (q=q_{\rm{s}})
\label{eq:vd2}
\end{equation}
where $A_1= \frac{24{\varepsilon_0}{\phi_{\rm{s}}}^2}{{\rho}}$ for the positively charged surface, $A_2= \frac{24{\varepsilon_0}{h_0}E{\phi_{\rm{s}}}}{{\rho}}$ for the negatively charged surface, $B_1= \frac{12{\varepsilon_0}E{\phi_{\rm{s}}}}{{\rho}}$ for the positively charged surface, $B_2= \frac{12{\varepsilon_0}{h_0}E^2}{{\rho}}$ for the negatively charged surface, and $C=-2gh_0+{V_{\rm{0}}}^2$. Here $V_{\rm{0}}=0$ for the shared charge model and the isolated capacitors model.

For the patched charge model, the particle-particle repulsive force, electric force and the gravity worked during the dust lifting process. The energy conservation law could be written as:
\begin{equation}
\frac{q_{p}^{2}}{4\pi\varepsilon_{0}D}-\frac{q_{p}^{2}}{4\pi\varepsilon_{0}h_{0}}= \frac{1}{2}m{V_{\rm{z}}}^2+mgh_0-Eqh_{\rm{E}}.
\label{eq:energ2}
\end{equation}
Since $h_{0}\gg D$, the term $\frac{q_{p}^{2}}{4\pi\varepsilon_{0}h_{0}}$ could be neglected. And the term $\frac{q_{p}^{2}}{4\pi\varepsilon_{0}D}=\frac{1}{2}m{V_{\rm{0}}}^2$, which determines the initial velocity $V_{\rm{0}}$ near the surface at $h\gg D$. Then we can obtain $V_{\rm{z}}$ at $h_{0}$:
\begin{equation}
{V_{\rm{z}}}^2=A_{\rm{p}}{D^{-2}}+C_{\rm{p}},\ \ \ \ (q=q_{\rm{p}})
\label{eq:vd3}
\end{equation}
where $A_{\rm{p1}}= \frac{24{\varepsilon_0}{(0.5\phi_{\rm{p}}^{2}-\phi_{\rm{s}}\phi_{\rm{p}})}}{{\rho}}$ for the positively charged surface, $A_{\rm{p2}}= \frac{24{\varepsilon_0}(0.5\phi_{\rm{p}}^{2}+{h_0}E{\phi_{\rm{p}}})}{{\rho}}$ for the negatively charged surface, and $C_{\rm{p}}=-2gh_0$.

The above equations suggest that the vertical velocity at the monitoring position is a function of the grain diameter. For the patched charge model, the dust's initial velocity $V_{0}$ resulting from the particle-particle repulsive force due to the micro-cavity charging dominates the upward dust transportation if the surface was positively charged ($\phi_{\rm{p}} \gg \phi_{\rm{s}}$), since the electric force due to the sheath electric field was downward.

In these experiments, the diameters ($D$) and vertical velocities ($V_{\rm{z}}$) of anorthite particles were simultaneously measured at the height of 6 mm. Figure \ref{fig:VD95} shows the distributions of the particle size and their corresponding vertical velocity. As shown in Figure \ref{fig:VD95}, for small particles, especially those with diameters below 5 $\rm{\mu m}$, ${V_{\rm{z}}}$ is distributed in a wider range. Some particles were even accelerated to above 5 $\rm{m~s^{-1}}$. However, for all the particles larger than 15 $\rm{\mu m}$, the speeds were limited within 2 $\rm{m~s^{-1}}$. In addition, anorthite particles with diameters above 40 $\rm{\mu m}$ were probably formed by particle aggregation, whose speeds were always lower than 1 $\rm{m~s^{-1}}$ (not shown here). It is possible that there were still some slow-speed aggregated grains with diameters below 40 $\rm{\mu m}$ released by the surface electric field. The measured diameter for some aggregated grains can be regarded as the equivalent grain size of a new single particle. The experimental results show that the vertical velocities of all the lifted anorthite particles are well constrained by their diameters.

\begin{figure}
\epsscale{1.2}
\plotone{VD_40max.jpg}
\caption{Vertical velocity as a function of diameter of the anorthite particle. The red (charged positively) and green (charged negatively) curves are constructed for particles smaller than 40 $\rm{\mu m}$ based on Equations (\ref{eq:vd1}-\ref{eq:vd2}) and (\ref{eq:vd3}). Note that the solid lines show the relationship between ${V_{\rm{z}}}$ and $D$ according to the isolated capacitors model, the dashed lines show the relationship according to the shared charge model, while the dotted lines show the relationship according to the patched charge model ($\xi=10$, $T_{\rm{se}}=3$ eV). In addition, the green solid and dashed lines and the blue dotted line are the upper enveloping curve for particles smaller than 40 $\rm{\mu m}$ based on Equations (\ref{eq:vd1}-\ref{eq:vd2}) and (\ref{eq:vd3}), respectively.
\label{fig:VD95}}
\end{figure}

For all the particles with diameters below 40 $\rm{\mu m}$, seven curves in Figure \ref{fig:VD95} are constructed by Equations (\ref{eq:vd1}-\ref{eq:vd2}) and (\ref{eq:vd3}). In the first case, we assume that the surface was positively charged with a surface potential of $\phi_{\rm{s}}=1.5$ V. For the isolated capacitors model, taken $q={q_{\rm{ic}}}$ and ${V_{\rm{0}}}=0$ m/s, the red solid line is given in Figure \ref{fig:VD95}(a), where $A_1$ is 1.83$\times$10$^{-13}$ $\rm{m^4~s^{-2}}$ and $C$ is $-0.12$ $\rm{m^2~s^{-2}}$. While for the shared charge model, the red dashed line in Figure \ref{fig:VD95}(a) is based on ${\phi_{\rm{s}}}>0$, $q={q_{\rm{s}}}$, ${V_{\rm{0}}}=0$ m/s, and then $B_1$ is 1.02$\times$10$^{-10}$ $\rm{m^3~s^{-2}}$. The red dashed curve indicates that based on the shared charge model, all micron-sized anorthite particles cannot migrate. In the isolated capacitors model, anorthite particles with diameters smaller than 3.3 $\rm{\mu m}$ can move upward if we ignore the cohesive force, but only the particles with diameters smaller than 1.3 $\rm{\mu m}$ can reach the measurement point. This is not consistent with our experimental results.

In the patched charge model \citep{wang2016dust}, anorthite particles acquired a non-zero initial velocity, namely ${V_{\rm{0}}}>0$ m/s, due to the particle-particle repulsive force. Then the particles moved upward and reached the measurement point. Based on the patched charge model, a red dotted line is given in Figure \ref{fig:VD95}(b), using Equation (\ref{eq:vd3}) with $T_{\rm{se}}=3$ eV, $\xi=10$, and $A_{\rm{p1}}=$7.29$\times$10$^{-12}$ $\rm{m^4~s^{-2}}$. Although many data points stay below the curve, there are still a notable fraction of data points with velocities and diameters much larger than the prediction of this curve. To cover all the data points, according to the blue enveloping curve in Figure \ref{fig:VD95}(b), $A_{\rm{p1}}$ is 1.15$\times$10$^{-9}$ $\rm{m^4~s^{-2}}$, then one can get $\xi=113$, much larger than the proposed maximum value of $\xi=10$ observed in the electron beam of 120 eV \citep{wang2016dust}. $\xi=113$ means a charging potential up to $-\xi T_{\rm{se}}/e=-339$ V for these high-speed anorthite particles in the micro-cavity, the absolute value of which is close to $E_{\rm{0}}/e=350$ V.

It is also possible that the surface was negatively charged. For the negatively charged surface, two upper enveloping curves are constructed by Equations (\ref{eq:vd1}) and (\ref{eq:vd2}), as shown by the green solid and dashed lines in Figure \ref{fig:VD95}(a). Here, ${V_{\rm{0}}}$ is considered to be zero. The green solid line is based on the isolated capacitors model, and $A_2$ is 1.15$\times$10$^{-9}$ $\rm{m^4~s^{-2}}$. Then, we can get $E\phi_{\rm{s}}$, which is 2.36$\times$10$^{6}$ $\rm{V^2~m^{-1}}$. If $\phi_{\rm{s}}=-$350 V, then $E$ and $d$ are 6.75$\times$10$^{3}$ $\rm{V~m^{-1}}$ and 51.80 mm, respectively. Based on the premise that the electric field range is higher than the measured point ($d>h_0$), the maximum surface potential is $-$119 V. Then, $E$ is in the range of 6.75$\times$10$^{3}$--1.98$\times$10$^{4}$ $\rm{V~m^{-1}}$, and the corresponding potential ranges from $-$350 to $-$119 V. While the green dashed line in Figure \ref{fig:VD95}(a) is based on the shared charge model, and $B_2$ is 2.85$\times$10$^{-4}$ $\rm{m^3~s^{-2}}$. Then, $E$ is 1.08$\times$10$^{6}$ $\rm{V~m^{-1}}$, thereby the effective distance of the electric field should be equal to 0.32 mm, which is obviously inconsistent with the premise that $d>h_0$. This means that it is impossible to use the shared charge model to explain the migration of these high-speed anorthite particles.

According to the patched charge model \citep{wang2016dust}, the green dotted line, as shown in Figure \ref{fig:VD95}(b), is obtained with $T_{\rm{se}}=3$ eV, $\xi=10$ and $E=6.75\times10^{3}$ $\rm{V~m^{-1}}$, namely $A_{\rm{p2}}=$5.86$\times$10$^{-11}$ $\rm{m^4~s^{-2}}$. Some of the data sites outside the line, which means a higher $\xi$ or $E$ is needed. $Eh_0$ in the expression for $A_{\rm{p2}}$ represents the potential difference between the measured point and the sample surface. According to the blue enveloping curve as shown in Figure \ref{fig:VD95}(b), $A_{\rm{p2}}$ is 1.15$\times$10$^{-9}$ $\rm{m^4~s^{-2}}$. Here, we consider the possible potential difference to be $-$350, $-$250, $-$150, $-$50 V or 0 V, then the corresponding $\xi$ are 26, 34, 50, 84 or 112, respectively. The $\xi$ values extracted from both the positive and negative surface charging conditions are larger than the proposed maximum value of $\xi=10$ observed in the previous experiment with an electron beam of 120 eV \citep{wang2016dust}.

There may exist possible correlation between various $\xi$ values and incident electron beam energies and fluxes. In the micro-cavity, there are backscattered electrons besides the secondary electrons. If the source particles corresponding to the secondary electrons emission is positively charged, then the flux of secondary electrons could be significantly suppressed according to Equation (\ref{eq:Jse1}). Due to the high emission energy of backscattered electrons, the flux of backscattered electrons in the cavity is slightly decreased. In this case, the backscattered electrons could be the main charging current in certain micro-cavity in our experiment because of substantial backscattered electron yield of 0.2$-$0.3 at 350 eV. For a certain anorthite particle, it is possible that $\delta(E_0 + e{\phi_{\rm{s}}}) + \eta(E_0 + e{\phi_{\rm{s}}})<1$ due to fluctuations in its chemical composition or shape. As a result, a larger charging potential up to $-$350 V is possible. This senario is consistent with a large $\xi$ value of 26--113 (corresponding $-\xi T_{\rm{se}}/e=-$339--$-$78 V) extracted from our experiments. By assuming the maximum charging potential for a levitating anorthite particle, it is not surprising that the isolated capacitors model could describe the data in the case of a negatively charged surface. In this case, $q_{\rm{ic}}$ is the upper limit of $q_{\rm{p}}$. But the isolated capacitors model could not work if the surface was positively charged since in this case $\phi_{\rm{s}}$ is too small compared to the negative surface potential. It will be very interesting to measure the surface potential in the later experiment to verify different model scenarios.

In a word, the isolated capacitors model and the patched charge model can effectively explain the current experimental data if the surface was negatively charged. In addition, the data below the blue enveloping curve denotes that $q<{q_{\rm{ic}}}$ or $q<{q_{\rm{p}}}$, that is, before being launched, a lot of particles did not obtain the saturated charge, which constrains the magnitude of the cohesive force between anorthite particles.

When $F_{\rm{c}}$ is the main driving force, the maximum size of lifted anorthite particles on the lunar surface may increase due to the reduced lunar gravity. When $F_{\rm{es}}$ is the main driving force, the maximum size of lifted anorthite particles on the lunar surface strongly depends on the electric field characteristics and the cohesive force between particles. The electrostatic field on the lunar surface could be lower than that in this experiment. This is caused by the lower incident electron current on the Moon, which means that the Debye length is significantly higher than that in our experiments. Generally, the Debye length on the Moon varies from dozens of centimeters to hundreds of meters. Based on Equations (\ref{eq:lambda0}) and (\ref{eq:nse}), for example, when the incident electron current on the Moon is reduced by 10000 times, the Debye length is increased by 100 times (0.17 m). However, it would become shorter for the surface with a higher secondary electron emission yield, especially in the space environment with a high electron flux and/or high electron energy, such as during the Moon's passage through the geomagnetic tail and during the solar burst period.

(2) Migration Height

When $\phi_{\rm{s}}>0$, $\lambda_{\rm{D}}<h_0$, based on the energy conservation law, the maximum rising height $H$ of anorthite particles can be written as:
\begin{equation}
H = {\frac{{{{V_{\rm{z}}}^2}}}{{2g}} + {h_0}}.
\label{eq:H1}
\end{equation}
When $\phi_{\rm{s}}<0$, $d>h_0$, for the particles that decelerated ($Eq<mg$) and cannot leave the electric field ($H<d$), the maximum rising height is
\begin{equation}
H = {\frac{{{{V_{\rm{z}}}^2}}}{{2g}}\cdot {\frac{mg}{mg-Eq}}+ {h_0}}.
\label{eq:H2}
\end{equation}
And for the particles that can leave the electric field range ($H>d$), the maximum rising height is
\begin{equation}
H = {\frac{{{{V_{\rm{z}}}^2}}}{{2g}} + {h_0}}+\frac{Eq}{mg}(d-h_0).
\label{eq:H3}
\end{equation}
The maximum rising height $H$ increases with the observed vertical velocity at the height of $h_0$. Figure \ref{fig:H}, for example, presents the distribution of $H$ derived from Equation (\ref{eq:H1}). The dust flux rapidly decreases with height. Nearly 70\% of the moving particles cannot reach a height of 5 cm. Particles with a migration height below 2 cm take up almost half of all lifted anorthite particles. It is worth noting that if the surface was negatively charged, the migration height will be even larger, according to Equations (\ref{eq:H1}-\ref{eq:H3}), than that when the surface was positively charged. Nonetheless, the results are supported by our measurements that numerous particles visible to the naked eye can only migrate to the heights of a few centimeters above the sample surface. In addition, 131 particles ($\sim$4.4\%) rose to heights above 25 cm, which impacted the chamber's ceiling. Half of them probably adhered to the ceiling or were scattered to other places, since only 70 particles ($\sim$2.4\%) that had reached heights above 25 cm, based on Equation (\ref{eq:H1}), returned the sample surface.

\begin{figure}
\epsscale{0.65}
\plotone{H.jpg}
\caption{Height distribution of lifted anorthite particles based on Eqation \ref{eq:H1}, where $V_{\rm{z}}$ was measured at the height of $h_0$ in our experiments. Note that $h_0$ was higher than $\lambda_{\rm{D}}$.
\label{fig:H}}
\end{figure}

On the lunar surface, dust grains can reach higher positions because of the lower gravitational acceleration. Based on Equation (\ref{eq:H1}), with one-sixth of Earth's gravitational acceleration ($g_{\rm{L}}=1/6g$) and identical electric field characteristics, the equivalent lifting height on the lunar surface is approximately six times that on Earth if dust grains satisfy $F_{\rm{es}}+F_{\rm{c}}>mg_{\rm{L}}+F_{\rm{co}}$. That is, only approximately 30\% of lifted particles can reach a height higher than 30 cm, while approximately 70\% of lifted particles migrate at a height below 30 cm. This result is consistent with the recent conclusion of a dust deposition upper line on rocks of approximately 28 cm \citep{yan2019weak}, and also matches well with the Surveyor LHG observations.

(3) Pulse Migration

The pulse migration of anorthite particles was found in these experiments. Several anorthite particles were detected almost simultaneously. The velocities of different anorthite particles are different from each other. The measurement point $h_{0}$ is 6 mm above the surface. Taking two typical emission velocities of 0.1 m/s and 0.5 m/s as an example, this implies that the emission time difference of the two anorthite particles are within 50 ms. It is not clear whether these anorthite particles were emitted at the same place, but it is possible in terms of the charging time of each dust particle. With a steady incident current ($I_{\rm{net}}$), the charging time ($\tau$) for a spherical particle can be given by $\tau I_{\rm{net}} = q$ \citep{lai2011fundamentals}, which can be obtained by $q=4\pi{\varepsilon _0}{r_{\rm{d}}}\phi_{\rm{g}}$ and $I_{\rm{net}}=J_{\rm{net}} \pi {D^2}/4$, where $\phi_{\rm{g}}$ is the grain's effective charging potential. $\phi_{\rm{g}}$ could be $\phi_{p}$ or $\phi_{s}$, depending on different models. Thus, the charging time for anorthite particles can be expressed by
\begin{equation}
\tau {\rm{ = }}\frac{{8{\varepsilon _0}{\phi_{\rm{g}}}}}{{{J_{\rm{net}}}D}}.
\label{eq:tau}
\end{equation}
The above equation shows $\tau \propto {D^{ - 1}}$ under the same incident flux condition. More time is needed to charge smaller anorthite particles to the equilibrium potential. Certainly, these particles may have been liberated before charging to saturation charges, that is, it takes less time than $\tau$. Based on Equation (\ref{eq:tau}), for example, in a vacuum environment of flux density 5 $A~{m^{-2}}$, a spherical surface of $R=1$ $\rm{\mu m}$ could be charged from 0 to 300 V in approximately 2 ms. Therefore, it is possible that anorthite particles in the same place were emitted one by one in a short time duration.
In addition, the interval between two pulse migrations ranged from 1 to 12 seconds in our experiments, which is distinctly longer than the emission time duration of the anorthite particles within one pulse migration.

The top surface may contain many dust aggregates, it is possible that the emission of one anorthite particle in the aggregates will decrease the cohesive forces of its neighboring particles, since the number of contacting particles for these neighboring particles could decrease due to the emission of this particle. Therefore, the emission of one anorthite particle could lead to a chain reaction, causing the emission of other particles in the aggregate in a short time duration, that is, pulse migration. A further detailed study of the micro-structure characteristics of the emission position of these pulse migrations may shed light on the emission mechanisms of dust particles. For example, one can check whether there are micro-cavities associated with the dust emission position as proposed by the patched charge model \citep{wang2016dust}.

\section{Conclusions}
To understand the interaction of incident electrons and dusty surface as well as the dust dynamics on the lunar surface, we measured the diameters and velocities of moving anorthite particles under electron beam irradiation with an energy of 350 eV for the first time. The measurements confirmed the vertical and horizontal migration of anorthite particles. Approximately 79\% of anorthite particles liberated by the electric field were smaller than 5 $\rm{\mu m}$. At the measurement point of 6 mm above the dusty surface, the speeds of approximately 90\% particles were lower than 2 m~s$^{-1}$ in the vertical direction and lower than 1 m~s$^{-1}$ in the horizontal direction. The average transport rates were principally in the range of 0.1--1.7 particles per second. Meanwhile, the pulse migration of multiple anorthite particles within very short-time duration (usually microseconds to tens of microseconds) was also observed. Further analysis about the surface micro-structures characteristics associated with this pulse migration may shed light on the dust emission mechanisms.

In our experiments, some anorthite particles were observed to have a large vertical velocity up to 9.74 m~s$^{-1}$ at the measurement point. The upper boundary of the vertical velocities $V_{\rm{z}}$ of these high-speed anorthite particles are well constrained by its diameter $D$, that is, $V_{\rm{z}}^2$ linearly depends on $D^{-2}$. To understand this relationship, we have discussed the surface potential, electric field intensity, and dust transport dynamics based on various models. The calculations reveal that the polarity of the bulk surface potential mainly depends on the secondary electron emission yield of the bulk sample surface, which is reduced by 2--3 times relative to that of an isolated particle. If the surface was charged positively, a typical surface potential was estimated to be 1.5 V. If the surface was charged negatively, the surface potential was not less than $-$350 V. The shared charge model could not explain the observed velocity-diameter data in our experiments no matter the surface was positively or negatively charged. The isolated capacitors model also largely underestimates the $V_{\rm{z}}$ and $D$ of the emitted anorthite particles if the surface was positively charged. But it could explain the emission velocity of these high-speed anorthite particles if the surface potential $\phi_{\rm{s}}$ is estimated to be between $-$350 and $-$119 V. Besides the above-mentioned two surface electric field acceleration model, the patched charge model, in which additional particle-particle repulsive force in the dust micro-cavity are considered, could explain the data no matter the surface was positively charged or negatively charged. However, a much larger effective charging potential ($-\xi T_{\rm{se}}/e$) of $-$339--$-$78 V for the dust charging in the micro-cavities should be utilized to reproduce the $V_{\rm{z}}$ and diameters data of the high-speed anorthite particles. Secondary electrons charging mechanism in the micro-cavities could be very hard to produce so large charging potential. For an incident electron energy of 350 eV, our experimental data may suggest an alternative charging mechanism from backscattered electrons which could produce much larger surface charges in the micro-cavity and stronger particle-particle repulsive force. In a word, the velocity-diameter data observed in our experiments provide strong constraints on various mechanisms related to dust charging and transportation. It would be very helpful to use these data to understand the dust charging and electrostatic transport mechanisms in airless celestial bodies such as the Moon and asteroids.

\acknowledgments
We acknowledge the National Natural Science Foundation of China (Nos. 41903058, 41931077, 11761161001) and the Science and Technology Development Fund (FDCT) of Macau (Nos. 007/2018/AFJ, 008/2017/AFJ, 0042/2018/A2). This work was also supported by the Strategic Priority Program of the Chinese Academy of Sciences (No. XDB41020300), the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the Key Research Program of the Chinese Academy of Sciences (No. XDPB11), the Beijing Municipal Science and Technology Commission (No. Z181100002918003) and the Scientific Research Program of Guizhou Institute of Technology (No. XJGC20181290).

redpajama_set_name: RedPajamaArXiv


text:
A's Fall to Springers, 9-2
COLD SPRING, Minn. � The Cold Spring Springers used 2 big innings, en route to a decisive 9-2 win over the Marshall A's on Sunday afternoon. Zach Olson (5-1) was dealt his first loss of the season, giving up 9 runs - 7 earned - in 3 1/3 innings.
The #2 seed Springers clinched a berth in Super Section play with the win, while the A's will now play the winner of Sauk Rapids and Brainerd for their ticket to move on.
Chace Pollock came into the game in relief of Olson and righted the ship, going 5 2/3 innings of scoreless ball.
Andrew Kinney went 1 for 3 with a double and run scored for the A's.
The A's will face off against the Sauk Rapids and Brainerd winner on Saturday afternoon at 1:00 pm. Winner qualifies for Super Section, while the loser's season will be over.
Cold Spring 4 0 0 5 0 0 0 0 0 9 15 2
Marshall A's 0 0 0 0 0 0 1 0 1 2 5 1
Players of the Game
Hitter
A. Kinney At Bats 3
Doubles 1
Runs Batted In 0
C. Pollock Innings Pitched 5.2
Earned Runs 0
Walks 2
Strikeouts 2
Hitters AB R H RBI BB SO AVG
Ben Korger, 3B 4 0 0 0 0 0 .305
Zach Olson, P 2 0 1 0 0 1 .419
--Ryan Engels, PH 2 0 0 0 0 1 .284
Andrew Kinney, 1B 3 1 1 0 1 0 .424
Derek West, CF 3 0 0 0 1 0 .353
Kyle Young, RF 3 1 1 1 1 0 .387
Cody Curry, LF 4 0 0 0 0 1 .321
Chace Pollock, SS 4 0 1 1 0 1 .250
Tyler Flattum, DH 3 0 1 0 0 2 .389
Taylor Rignell, 2B 2 0 0 0 0 1 .378
--Brandon Wilhelmi, PH 1 0 0 0 0 1 .270
2B - Andrew Kinney (13)
3B - None
HR - None
SB - None
HBP - None
Pitchers IP H R ER BB SO HR ERA
Zach Olson (L, 5-1) 3.1 9 9 7 0 3 0 3.51
Chace Pollock 5.2 6 0 0 2 2 0 1.31
TOTALS 9.0 15 9 7 2 5 0
HB - Zach Olson (5)
WP - None

redpajama_set_name: RedPajamaCommonCrawl


Hurricane Tracker By HurricaneSoftware.com's - iHurricane Free by GenCode Systems, Inc.
iHurricane by HurricaneSoftware.com Is The Most Popular Hurricane Tracking App For iPhone/iPad and iTouch.
- From Developers of the most downloaded Hurricane Tracking App iHurricane this is a Pro version of iHurricane that runs in native iPhone and NOW iPad screen resolutions.
- iHurricane HD is the only one that lets you use our app for free. The way InApp purchase works is if you like the app you can purchase the extra features of Push and extended content. Other apps make you purchase before you can even use the app. InApp purchase lets you really get to know the app your buying before you buy. Your purchase goes toward both the iPhone and iPad resolutions.
- Only Hurricane app that tracks Multiple (not just one at a time) Hurricanes on a interactive map!
- Only Hurricane app with PUSH!
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-Get distance between your location and EACH coordinate of the storm!
- Fully interactive map with clickable icons!
- Created by HurricaneSoftware.com, developer of PC Computing Best Of The Net Award!
Fully interactive map, more images, and more features than the others.
iHurricane HD is a Hurricane Tracking System that integrates with HurricaneSoftware.com's applications to give you the most up to-date and reliable hurricane coordinates data and high resolution maps. Using GeoLocation you will be able to tell how far an active storm is from you in miles at any moment, see satellite images of active storms. Get information such as wind-speed, millibars and much more.
- Distance from your location to storms location in miles.


October 22, 2016 - Like us now!
foodpanda, ecommerce platform for food delivery, has celebrated its 4th anniversary with a vow to ace 400 million USD food delivery market in Pakistan.
The grand event hosted by foodpanda Pakistan on its 4th Anniversary was something that turned on even the faint-hearted. The celebration was graced by the top Customers of foodpanda, CEO's of top hospitality brands in the country, food & lifestyle Bloggers and leading Celebrities from the industry – who by the way happen to be ardent users of foodpanda.
What started in 2012 as a fusion of innovation and experience – was bound to tantalize the taste buds of the entire nation. And it didn't disappoint! Such positive was the response that in a short period of four years, foodpanda catered to half a million hungry foodies and generated Rupees one billion additional revenue for the restaurant industry.
The food delivery market in Pakistan is estimated to reach a 400 Million USD mark by 2020; thanks to healthy economic growth in the country, improved law and order situation, increased penetration of 3G and 4G services and increased investments, especially in the hospitality sector. Local restaurant heroes are expanding their footprint across the country and international chains are eyeing second tier cities for expansion.
In such a thriving industry landscape, foodpanda is playing a vital role in connecting millions of foodies in Pakistan with their all-time favorite eateries like McDonald's, KFC, Nando's, Dunkin Donuts, Johny Rockets, Fat Burger, Sarpinos, OPTP and many more.
Using foodpand's cutting-edge, user-friendly mobile App, customers are able to discover all the restaurants delivering to their area and restaurants are able to attract a customer base that usually does not order using the existing ordering channels. More than a 100% spike in App downloads only in last 12 months is a true evidence of foodpanda's popularity among the local foodies.


What's going on at Epcot?
The Millennium Celebration begins October 1, 1999 and continues until January 1, 2001. The event can be compared to WDW's 25th Anniversary Celebration in terms of size and scope. Epcot will be the host location, with most of the events taking place within the park. This is a preliminary list of the changes to our favorite park, some already started, and some which will be undertaken this Summer. This list is by no means official - the information has been collected from Disney press releases, Cast Members, and general rumors. Changes are listed in the order you would encounter them as you walk through the park.
The parking toll booth area is scheduled to be rehabbed with a new look and the removal of most 1982 cladding and signage. The parking lot repaving and realignment was completed in 1998.
The entire area is supposed to receive a complete rehab, with new signage and a more modern look. A proposed "Legacy Walk" will be much like the Magic Kingdom's Walk around the World, only with metal or aluminum plates instead of bricks. The ticket booths recently received a new coat of paint, so it looks as though they will stay pretty much the same. The entrance plaza in front of Spaceship Earth will be closed all Summer long while these marble sculpture-things are built to replace the old gardens. The fountain has been removed, including the plexiglass sculptures.
Update: Thanks to Dave, below is an imagineering concept drawing of a giant (we're talking 150 feet!) Mickey hand and wand reaching over Spaceship Earth. So I suppose the rumors are true! BTW, that's Marty Sklar, Imagineering boss, in the foreground. As of mid-Summer, a huge mass of blue steel framing was sitting in the east parking lot being constructed, presumably to position beside Spaceship Earth when ready. It looks to be about 140 feet tall.
The plans are to cover the entire Innoventions Plaza with a cable and canvas 'tent'. The rigging is already done, and most of the cables are being put in place. The material will be blue or purple and will look like a chess board as opposed to a full cover. Under the dome, displays and stages will be set up. This will presumably be the headquarters of the Celebration, and where the Opening Ceremonies will take place. The Opening Ceremonies have been described as near the scope of the Olympics opening, with hundreds of performers, original music, and special surprises. Replacing the current jets in the Fountain of Nations is a rumored possibility. As of late 1998, preliminary work was being done on the area, with the entrance to Innoventions West removed.
A new Centorium will take over all of Innoventions East, South side. The new store will apparently be the largest in-park merchandise location at WDW. The Epcot Outreach/Discovery Center was closed to make room for the expansion. As usual, new exhibits will be continually added to both sides of Innoventions, since there is still a large amount of unoccupied space, including a theater, I believe.
Horizons closed January 9, 1999. However, the pavilion has remained mothballed, and untouched. That leaves the possibility of re-opening the ride during peak times, or even rehabbing the original ride for the Millennium. Disney claims it will not reopen, and they are imagineering a new concept. The catch is that a corporate sponsor is needed before any work can be done - GE's departure was the reason Horizons closed in the first place. Intel and Boeing are rumored to be interested. The pavilion will have a space theme, and possibly use the two OmniMax screens from the ride (which actually hold the building up) as a simulator experience akin to Back to the Future or Star Trek: The Experience.
Now that the ride is operational, work is being done to improve reliability and capacity. Hopeful it will be up to spec by Oct. 1.
Since closing in the Fall of 1998, the former imagination ride building has been gutted and construction is continuing on a new attraction. Possibly using the old ride system (with some improvements so the cars don't always hit each other), the new ride will take guests through a child's imagination. Themed as a part of the Imagination Institute (from HISTA) the new ride will keep Figment, but ditch Dreamfinder. The Image Works area upstairs will be converted to a display area much like the new Camera Center in MK, with Kodak Image Technologies. Opening is scheduled for October 1, 1999 with CM soft openings in late Summer.
Main tank renovations of the shell base and filtration system were completed in 1998. Coral Reef Restaurant renovations completed 1998.
A parade will wind its way around the promenade twice daily. Featuring performers from each country, Epcot entertainment performers and larger-than-life figures, with a new original soundtrack. Also, installation of huge torches around the promenade will be done this Summer, illuminating the promenade with something a lot nicer than those awful light towers. Most of the bases for these are in place (they sit in the water) and at least one torch, with a medieval-look, is erected and operational.
Illuminations 2000 (or something similar) will debut October 1. The likelihood is that the current show will go down in June to allow construction of the new performance. Testing has been ongoing since Summer 1998, when selected effects were tested before park opening or incorporated into the nightly performances to gauge effectiveness. Effects included a barrage of very loud explosions, increasing in frequency to a crescendo - known as the 'big bang'. Another effect is huge fireball which is supposed to rise into the air and then explode. The old rusty barges will be destroyed (shouldn't be too hard), and a new soundtrack will be recorded. Four new anchors have been built in early 1999 around the lagoon for the new show. Backstage, behind American Adventure, work is proceeding on the Millennium Sphere, a large object that will presumably be the centerpiece in the new show.
El Rio del Tiempo will close shortly to be reopened with a new theme. The boat ride will be taken over by the Three Caballeros with new sets, animatronics, and effects and will presumably open in time for the Millennium Celebration.
A Biergarten rehab has been planned and budgeted for years now, maybe 1999 will be the year Germany foods finally gets their funding. The plans call for a marche-style German market, with individual stations in a market atmosphere.
Although not part of the Millennium Celebration, this Summer Michael Flatley's Lord of the Dance will be performed four times daily with a four-month run. A new Millennium show will debut October 1, 1999.
New film? Le Cellier was renovated in late 1998 and is now open. A new merchandise location selling Roots apparel and accessories is open. The Refreshment Port restrooms will be rebuilt to accommodate the increased traffic from the new pavilion next door.
Update: Rumors from the Canada pavilion are that McDonalds may be involved in a Port rehab. "Would you like fries with that?"


text:
What are the Different Types of Quad Bike?
Dan Cavallari
Last Modified Date: December 28, 2022
The two most common quad bike models are racing quad bikes and all terrain vehicle (ATV) quad bikes that are more utilitarian. A racing quad bike will generally be lighter than other types of ATV models, and the specific components are designed for the rigors of racing. More utilitarian quad bike models are often much larger and heavier, and they are meant to perform extra duties such as hauling large amounts of weight, towing, and traveling longer distances. Racing models are also typically two-wheel drive, while ATV models are very often four-wheel drive. Other models of quads exist, such as amphibious quads or modified sport utility quads.
A racing quad bike will usually be two-wheel drive, much lighter than other models of quad, and feature a lower center of gravity for quick cornering and stability. The components of such a quad bike will be designed for effective racing; suspension, for example, may be adjustable to accommodate a course with several jumps or a flatter course with muddy conditions. Tires can also be replaced to suit the conditions of the race course. The engines are designed to have high power output to enhance speed capabilities during racing.
ATV quad bikes are designed for rough terrain.
More utilitarian ATV quad bike models are bulkier and less adapted for speed. They are designed with strength, comfort, and usability in mind. An ATV quad bike may feature gear racks or gun racks, more paneling and fairing to protect the rider and the bike from mud and debris, accessories such as winch systems and trailer hitches, and other convenient features such as rear view mirrors and headlights. Such quads are almost always four-wheel drive to accommodate for rough terrain and excess weight being carried on the vehicle. It is not uncommon to see models with automatic transmissions rather than manual transmissions common on other types of bikes.
An on-road bike is equipped with headlights.
An amphibious ATV is one that is designed to handle both off-road capabilities as well as water capabilities. They are useful in swamps and marshes, and while four-wheel models do exist, they are quite rare. Six or eight wheel models are more common, and some amphibious vehicles even feature tracks similar to those of a tank rather than wheels.
Sport utility ATV models are often styled after utilitarian models, but they sometimes feature other types of conveniences, such as protective canopies and seating for more than one person. Most quad models are meant to be ridden by only one person, but sport utility ATVs sometimes feature longer wheel bases that allow more rider room to accommodate a passenger and driver.
What Are the Different Types of ATV Snorkel Kits?
What Are ATV Tracks?
What Are the Different Types of ATV Bikes?
What Is a Wheel Winch?
What Is an Amphibious Vehicle?
What are Road Legal Quad Bikes?
What are the Different Types of Quad Bike Parts?
By: Tomasz Sibilski
By: aigarsr
A racing quad bike is usually lighter and more streamlined than other quad bike models.


text:
GARY COOPER Quiz — The Answers
August 4, 2015Written by Joe Morella and Frank Segers
Gary Cooper won two best-actor Academy Awards, but his third Oscar — an honorary one presented in 1961, the year he died of cancer at age 60 — is the most telling.
It cites his career filled with "many memorable screen performances." Too sick at the time to attend the official ceremonies, the special Oscar was accepted on Cooper's behalf by his friend, James Stewart. It was an emotional Hollywood farewell for one of its greatest stars.
Cooper began making movies in 1926, and continued right up until the year he died. As mentioned yesterday, it's time to brush up on his career given that he has been gone for more than a half century.
Which brings us to our Monday Quiz. Let's see how you did. (To refresh yourselves about the questions, just scroll down to the blog below). Here we go:
1) Answer: c) Cooper's agent picked out "Gary" as his billed first name because it had a nice sound and reminded him of the steel town of Gary, Indiana.
2) Answer: a) Cooper's first talking movie, 1929's The Virginian, established the actor as a bona fide Western hero. It was a career breakthrough.
3) Answer: b) Lupe Velez, known as the "Mexican spitfire," dumped Cooper in favor of former Olympic swimming star Johnny Weissmuller.
4) Answer: Patricia Neal, who in the late 40s had with Cooper one of the steamiest affairs going. But he wouldn't leave his wife for her. Years later Neal suffered a debilitating stroke, which affected her speech. Her recovery was much publicized, especially when Neal took to making coffee commercials on tv.
5) Answer: a) and b), 1952's High Noon and 1941's Sergeant York.
6) Answer: a) True. Both Cooper's parents were English, who had immigrated to the U.S. by the time the actor was born in 1901 in Helena, Montana. Cooper himself lived in Britain from 1910 to 1917. Cooper's sole wife was socialite Veronica Balfe, who acted under the name of Sandra Shaw. Their daughter is socialite Maria Cooper.
7) Answer: a) True. Contrary to her "Princess" image, Grace Kelly really got around early in her Hollywood career. She was 22 when she played opposite Cooper in High Noon, and is believed to have carried on with both the actor and the picture's director Fred Zinnemann — at the same time.
8) Answer: a) Stagecoach and b) Gone With The Wind.
9) Answer: Lee Van Cleef.
10) Answer: b) False. Cooper and Audrey Hepburn, costars of Billy Wilder's 1957 romance Love in the Afternoon, maintained an affectionate but strictly professional relationship.
The Perfect Child Star — And We Don't Mean Shirley.
Monday Quiz — GARY COOPER
Son of Rusty Shackleford
I love the story that Cooper always carried a checkbook with him (when it wasn't common to do that) and would pay at gas stations, restaurants, etc. by check for relatively small amounts. The proprietors were so proud to get a signed check by Gary Cooper that they'd frame them on the wall of the business where all the customers could see it….and never cash the check, thus saving Cooper the cost of the product.


text:
Q: MongoDB $elemMatch on ALL embedded documents/subdocuments I have the following students collections:
[
  {
    nickname: 'Hafez',
    classes: [
      { name: 'Physics', score: 5 },
      { name: 'Math', score: 10 }
    ]
  },
  {
    nickname: 'Nada',
    classes: [
      { name: 'Physics', score: 8 },
      { name: 'Math', score: 9 }
    ]
  },
  {
    nickname: 'Sam',
    classes: [
      { name: 'Physics', score: 6 },
      { name: 'Math', score: 10 }
    ]
  }
]

I am trying to get the students that scored at least 7 in all classes.
The following filter gives me all documents because they all have scored 7 in some class. I want to find them only if they scored 7 in all classes.
Student.find({ 'classes.score': { $gte: 7 } }); // incorrectly finds all students.

A: The solution I found is to inverse the condition and do a $not.
The following says: find me a student who has not scored less than 7 in any class, which is the equivalent of "find me all students who scored higher than 7 on all classes.
Student.find({
  'classes.score': {
    $not: {
      $lt: 7
    }
  }
}); // correctly logs only `Nada`

Admittedly, the readability of this is quite difficult to grasp and you'll often have to explain it to your peers why you're doing this the way you are, but I couldn't find any other way to achieve what I am trying to achieve.
Here's a mongo playground to play with this: https://mongoplayground.net/p/4hI3j7dliYw

redpajama_set_name: RedPajamaStackExchange


text:
IPW Webinar: Multi-Jurisdiction Patent Litigation: A Global Affair
December 15, 2020 @ 12:00 pm - 1:00 pm EST
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For a patent owner seeking to enforce one— or many— patents, understanding the web of jurisdictions available to them can be difficult. While all jurisdictions offer a variety of opportunities and advantages, none is ideal. In order to make a strong strategic decision, it is imperative that patent owners understand the balance between risks and benefits for each jurisdiction.
The United States is known internationally for greater discovery, but even within the U.S. there are significant variations. The U.S. International Trade Commission can offer exclusion orders and cease and desist orders, the Patent Trial and Appeal Board can invalid patents and frequently does just that, and district courts across the country range from patent owner friendly in the Eastern and Western Districts of Texas, to district courts that can be rather inhospitable to patent owners, particularly when they are suing large multinational corporations.
Just as critically, these variations exist on a global scale as well. The United Kingdom has shown a willingness to award worldwide royalties, in China successful patent owners receive injunctions in almost all cases, many increasingly find Germany the best of all worlds, but others will say it is no panacea.
Patent litigation is increasingly a multi-jurisdiction, cross border affair that requires strategic consideration.
Join Gene Quinn, President, Founder & CEO of IPWatchdog, Inc. and three-time Global Top 50 Most Influential People in IP, on Tuesday, December 15, 2020, at 12 pm (noon) EST, for a wide-ranging conversation that will discuss the many faces and facets of patent litigation in the United States and across the globe. Joining Gene will be Zoe Butler from Powell Gilbert, David Marques from Darts-ip, and Christine Yun Sauer from Robins Kaplan LLP.
Christine Yun Sauer, Clarivate, David Marques, Gene Quinn, Zoe Butler
Post a Premium Event $199 $69 (Limited Time)


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the Warmup Wetroom System must be installed by trained applicators, approved by Warmup New Zealand Ltd.
Clause B2 DURABILITY: Performance B2.3.1 (b), 15 years for substrates to wet areas. Warmup Wetroom System meets these requirements.
Clause E3 INTERNAL MOISTURE: Performance E3.3.4, E3.3.5 and E3.3.6. Warmup Wetroom System meets these requirements.
Clause F2 HAZARDOUS BUILDING MATERIALS: Performance F2.3.1. Warmup Wetroom System meets this requirement and will not present a health hazard to people.
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No special conditions or limitations. Refer to the Appraisal for general requirements.
For a copy of the Technical Literature please contact Warmup New Zealand Ltd or click on the link to the left.
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