How often do solar flares occur?
Solar flare
Other large solar flares also occurred on April 2, 2001 (X20), October 28, 2003 (X17.2 and 10), September 7, 2005 (X17), February 17, 2011 (X2), August 9, 2011 (X6.9), March 7, 2012 (X5.4), July 6, 2012 (X1.1). On July 6, 2012, a solar storm hit just after midnight UK time, when an X1.1 solar flare fired out of the AR1515 sunspot. Another X1.4 solar flare from AR 1520 region of the Sun, second in the week, reached the Earth on July 15, 2012 with a geomagnetic storm of G1–G2 level. A X1.8-class flare was recorded on October 24, 2012. There has been major solar flare activity in early 2013, notably within a 48-hour period starting on May 12, 2013, a total of four X-class solar flares were emitted ranging from an X1.2 and upwards of an X3.2, the latter of which was one of the largest year 2013 flares. Departing sunspot complex AR2035-AR2046 erupted on April 25, 2014 at 0032 UT, producing a strong X1.3-class solar flare and an HF communications blackout on the day-side of Earth. NASA's Solar Dynamics Observatory recorded a flash of extreme ultraviolet radiation from the explosion. The Solar Dynamics Observatory recorded an X9.3-class flare at around 1200 UTC on September 6, 2017.
Superflare
Superflare stars show a quasi-periodic brightness variation, which is interpreted as evidence of starspots carried around by solar rotation. This allows an estimate of the rotation period of the star; values range from less than one day up to tens of days (the value for the Sun is 25 days). On the Sun, radiometer monitoring from satellites shows that large sunspots can reduce the brightness by up to 0.2%. In superflare stars the most common brightness variations are 1-2%, though they can be as great as 7-8%, suggesting that the area of the starspots can be very much larger than anything found on the Sun. In some cases the brightness variations can be modelled by only one or two large starspots, though not all cases are so simple. The starspots could be groups of smaller spots or single giant spots.
Superflare
Kepler data have also been used to search for flares on stars of later spectral types than G. A sample of 23,253 stars with effective temperature T less than 5150K and surface gravity log g > 4.2, corresponding to main sequence stars later than K0V, was examined for flares over a time period of 33.5 days. 373 stars were identified as having obvious flares. Some stars had only one flare, while others showed as many as fifteen. The strongest events increased the brightness of the star by 7-8%. This is not radically different from the peak brightness of flares on G-type stars; however, since K and M stars are less luminous than type G, this suggests that flares on these stars are less energetic. Comparing the two classes of stars studied, it seems that M stars flare more frequently than K stars but the duration of each flare tends to be shorter. It is not possible to draw any conclusions about the relative proportion of G and K type stars showing superflares, or about the frequency of flares on those stars that do show such activity, since the flare detection algorithms and criteria in the two studies are quite different.
List of solar storms
Solar storms of different types are caused by disturbances on the Sun, most often coronal clouds associated with coronal mass ejections (CMEs) produced by solar flares emanating from active sunspot regions, or, less often, from coronal holes. Solar filaments (solar prominences) may also trigger CMEs, trigger flares, or occur in conjunction with flares, and associated CMEs can be intensified.
Hyder flare
The explanation for these solar flares comes from Hyder’s two-fold observations. One, flares tended to have a parallel ribbon shape to them with one on either side of the filament channel. Two, these flares were not caused by or associated with geomagnetic storms. 
Quiescent filaments have been believed to belong to a magnetic trough, which can disappear due to the field’s reconfiguration. When this happens, the filamentary material is said to be thrown into the corona, creating a typical solar flare. Hyder explains that the process for Hyder flares differs, in that sometimes the filamentary material instead cascades down the outer sides of the elevated magnetic trough, or ridge, to interact with the lower chromospheric material that is producing the flare. If this falling process is not symmetrical on either side, then there will be a double parallel ribbon shape form, whereas a symmetrical fall will produce only a single parallel ribbon. A sporadic or insufficient fall of filamentary material will cause bright knots of solar flares to be produced.
Solar cycle 21
Solar cycle 21 was the 21st solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 10.5 years, beginning in March 1976 and ending in September 1986. The maximum smoothed sunspot number (SIDC formula) observed during the solar cycle was 232.9, in December 1979, and the starting minimum was 17.8. During the minimum transit from solar cycle 21 to 22, there were a total of 273 days with no sunspots. The largest solar flare of this cycle (X15) occurred on July 11, 1978.
Solar flare
Flare sprays are a type of eruption associated with solar flares. They involve faster ejections of material than eruptive prominences, and reach velocities of 20 to 2000 kilometers per second.
Solar eclipse
Total solar eclipses are rare events. Although they occur somewhere on Earth every 18 months on average, it is estimated that they recur at any given place only once every 360 to 410 years, on average. The total eclipse lasts for only a maximum of a few minutes at any location, because the Moon's umbra moves eastward at over 1700 km/h. Totality currently can never last more than 7 min 32 s. This value changes over the millennia and is currently decreasing. By the 8th millennium, the longest theoretically possible total eclipse will be less than 7 min 2 s. The last time an eclipse longer than 7 minutes occurred was June 30, 1973 (7 min 3 sec). Observers aboard a Concorde supersonic aircraft were able to stretch totality for this eclipse to about 74 minutes by flying along the path of the Moon's umbra. The next total eclipse exceeding seven minutes in duration will not occur until June 25, 2150. The longest total solar eclipse during the 11,000 year period from 3000 BC to at least 8000 AD will occur on July 16, 2186, when totality will last 7 min 29 s. For comparison, the longest total eclipse of the 20th century at 7 min 8 s occurred on June 20, 1955, and there are no total solar eclipses over 7 min in duration in the 21st century.
Solar particle event
Extremely intense solar proton flares capable of producing energetic protons with energies in excess of 100 MeV can increase neutron count rates at ground levels through secondary radiation effects. These rare events are known as Ground Level Enhancements(or GLEs). Some events produce large amounts of HZE ions, although their contribution to the total radiation is small compared to the level of protons.Contribution of High Charge and Energy (HZE) Ions During Solar-Particle Event of September 29, 1989 Kim, Myung-Hee Y.; Wilson, John W.; Cucinotta, Francis A.; Simonsen, Lisa C.; Atwell, William; Badavi, Francis F.; Miller, Jack, NASA Johnson Space Center; Langley Research Center, May 1999.
Solar cycle 24
Then, on September 22, an X1.4-class solar flare erupted out of sunspot 1302. A R3-level radio blackout was registered. The blast produced a significant CME, but was not Earth directed. Two days later, an X1.9-class flare followed in the next 31 hours by a spectacular string of 14 M-class flares, being the biggest two M7 flares, were mostly unleashed out of the same sunspot. The first two explosions, X1.9 and M7.1, propelled a pair of closely spaced CMEs. A G4 (severe) geomagnetic storm was reported on September 26.
Inex
An inex also is close to an integer number of days (10,571.95) so solar eclipses on average take place at about the same geographical longitude at successive events, although variations of the moon's revolutionary speed at different points of the eclipse mask this relation. In addition sequential events occur at opposite geographical latitudes because the eclipses occur at opposite nodes. This is in contrast to the better known saros, which has a period of about days, so successive solar eclipses tend to take place about 120° in longitude apart on the globe (although at the same node and hence at about the same geographical latitude).
Solar flare
Flares occur when accelerated charged particles, mainly electrons, interact with the plasma medium. Evidence suggests that the phenomenon of magnetic reconnection leads to this copious acceleration of charged particles.
On the Sun, magnetic reconnection may happen on solar arcades – a series of closely occurring loops following magnetic lines of force. These lines of force quickly reconnect into a lower arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy in this reconnection is the origin of the particle acceleration. The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a coronal mass ejection. This also explains why solar flares typically erupt from active regions on the Sun where magnetic fields are much stronger.
Solar eclipses on Uranus
Solar eclipses on Uranus occur when any of the natural satellites of Uranus passes in front of the Sun as seen from Uranus. Eclipses can occur only near a solar ring plane-crossing of Uranus (equinox), occurring approximately every 42 years, with the last crossing being in 2007/2008.
Solar phenomena
A coronal mass ejection (CME) is a massive burst of solar wind and magnetic fields rising above the solar corona. Near solar maxima, the Sun produces about three CMEs every day, whereas solar minima feature about one every five days. CMEs, along with solar flares of other origin, can disrupt radio transmissions and damage satellites and electrical transmission line facilities, resulting in potentially massive and long-lasting power outages.
Solar flare
In addition to these solar observing facilities, many non-solar astronomical satellites observe flares either intentionally (e.g., NuSTAR), or simply because the penetrating hard radiations coming from a flare can
readily penetrate most forms of shielding.
Human spaceflight
Without proper shielding, the crews of missions beyond low Earth orbit (LEO) might be at risk from high-energy protons emitted by solar flares and associated solar particle events (SPEs). Lawrence Townsend of the University of Tennessee and others have studied the overall most powerful solar storm ever recorded. The flare was seen by the British astronomer Richard Carrington in September 1859. Radiation doses astronauts would receive from a Carrington-type storm could cause acute radiation sickness and possibly even death. Another storm that could have incurred a lethal radiation dose if astronauts were outside the Earth's protective magnetosphere occurred during the Space Age, in fact, shortly after Apollo 16 landed and before Apollo 17 launched. This solar storm of August 1972 would likely at least have caused acute illness.
Kappa1 Ceti
According to recent hypotheses, unusually intense stellar flares from a solar twin star could be caused by the interaction of the magnetic field of a giant planet in tight orbit with that star's own magnetic field. Some Sun-like stars of spectral class F8 to G8 have been found to undergo enormous magnetic outbursts to produce so-called superflares (coronal mass ejections) that release between 100 and 10 million times more energy than the largest flares ever observed on the sun, making them brighten briefly by up to 20 times. In 1998, nine Solar twin stars (including Kappa Ceti) were observed to have produced superflares, on average, about once per century. None of these stars rotate particularly fast, have close binary companions, or are very young. Previously, such large flares had not been observed in solar-type main sequence stars, although they are common in a group of dim main-sequence, reddish M dwarfs known as flare stars.
Solar eclipse of August 22, 1998
An annular solar eclipse occurred on August 22, 1998. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible in Indonesia, Malaysia, Papua New Guinea, Solomon Islands (Bellona Island and Rennell Island) and Vanuatu.
Corona
Flares take place in active regions and are characterized by a sudden increase of the radiative flux emitted from small regions of the corona. They are very complex phenomena, visible at different wavelengths; they involve several zones of the solar atmosphere and many physical effects, thermal and not thermal, and sometimes wide reconnections of the magnetic field lines with material expulsion.
Solar eclipse of July 1, 2000
A partial solar eclipse occurred on July 1, 2000. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A partial solar eclipse occurs in the polar regions of the Earth when the center of the Moon's shadow misses the Earth.
This eclipse occurred near the south pole, and was visible from the southern tip of South America at sunset.
Solar eclipse of November 23, 1965
An annular solar eclipse occurred on November 23, 1965. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from the Soviet Union (today's eastern Turkmenistan, southern Uzbekistan and southwestern Tajikistan), Afghanistan, Pakistan, India, China, Nepal (including the capital city Kathmandu), southwestern Sikkim (now merged with India), Burma, southwestern tip of Sainyabuli Province in Laos, Cambodia, South Vietnam (now belonging to Vietnam), Spratly Islands, Brunei, Malaysia, Indonesia, the Territory of Papua New Guinea (today's Papua New Guinea), and Gilbert and Ellice Islands (the part now belonging to Kiribati). 8 of the 14 eight-thousanders—Dhaulagiri, Annapurna, Manaslu, Shishapangma, Cho Oyu, Everest, Lhotse and Makalu, as well as the highest peak of Oceania, Puncak Jaya, lie in the path of annularity.
Superflare
Flares are more common in stars with short periods. However, the energy of the largest flares is not related to the period of rotation. Stars with larger variations also have much more frequent flares; there is as well a tendency for them to have more energetic flares. Large variations can be found on even the most slowly rotating stars: one star had a rotation period of 22.7 days and variations implying spot coverage of 2.5% of the surface, over ten times greater than the maximum solar value. By estimating the size of the starspots from the amplitude variation, and assuming solar values for the magnetic fields in the spots (1000 G), it is possible to estimate the energy available: in all cases there is enough energy in the field to power even the largest flares observed. This suggests that superflares and solar flares have essentially the same mechanism.
Satellite flare
Flares may also occur from solar panels, but they are not as bright (up to −3.5 magnitude). Such flares last about twice as long as those from the main mission antennas (MMA), because the so-called "mirror angle" for the solar panels is twice that for the MMAs. There are also rare cases of flares from MMAs and solar panels, or two MMAs (front and either right or left) of one satellite in a single pass.
Solar Saros 127
Solar Saros 127, repeats every 18 years, 11 days, contains 82 events in which 40 will be partial eclipses and 42 will be total. There are no annular or hybrid eclipses in this series. Lunar Saros 120 interleaves with this solar saros with an event occurring every 9 years 5 days alternating between each saros series.
Superflare
In order to determine whether superflares can occur on the Sun, it is important to narrow the definition of Sun-like stars. When the temperature range is divided into stars with T above and below 5600K (early and late G-type stars), stars of lower temperature are about twice as likely to show superflare activity as those in the solar range and those that do so have more flares: the occurrence frequency of flares (number per star per year) is about five times as great in the late-type stars. It is well known that both the rotation rate and the magnetic activity of a star decrease with age in G-type stars. When flare stars are divided into fast and slow rotators, using the rotation period estimated from brightness variations, there is a general tendency for the fastest-rotating (and presumably youngest) stars to show a greater probability of activity: in particular, stars rotating in less than 10 days are 20-30 times more likely to have activity. Nevertheless, 44 superflares were found on 19 stars with similar temperatures to the Sun and periods greater than 10 days (out of 14000 such stars examined); four superflares with energies in the range 1-5 × 10 ergs were detected on stars rotating more slowly than the Sun (of about 5000 in the sample). The distribution of flares with energy has the same shape for all classes of star: although Sun-like stars are less likely to flare, they have the same proportion of very energetic flares as younger and cooler stars.
Solar phenomena
Solar phenomena are the natural phenomena occurring within the magnetically heated outer atmospheres in the Sun. These phenomena take many forms, including solar wind, radio wave flux, energy bursts such as solar flares, coronal mass ejection or solar eruptions, coronal heating and sunspots.
Solar eclipse of October 22, 1911
An annual solar eclipse occurred on October 22, 1911. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from the Russian Empire (the parts now belonging to Kazakhstan, Uzbekistan and Kyrgyzstan), China, French Indochina (the part now belonging to Vietnam), Philippines, Dutch East Indies (today's Indonesia), Territory of Papua (now belonging to Papua New Guinea) including the capital city Port Moresby, and British Western Pacific Territories (the parts now belonging to Solomon Islands and Tuvalu, including the city of Honiara and Tulagi).
Helium flash
A helium flash is a very brief thermal runaway nuclear fusion of large quantities of helium into carbon through the triple-alpha process in the core of low mass stars (between 0.8 solar masses () and 2.0 ) during their red giant phase (the Sun is predicted to experience a flash 1.2 billion years after it leaves the main sequence). A much rarer runaway helium fusion process can also occur on the surface of accreting white dwarf stars.
Solar eclipse of September 23, 1987
An annular solar eclipse occurred on September 23, 1987. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible in the Soviet Union (today's Kazakhstan), China (including Shanghai), southwestern Mongolia, Okinawa Islands of Japan except Kume Island and the southwestern tip of Kerama Islands, the Federal States of Micronesia, Papua New Guinea, Solomon Islands, Rotuma Islands of Fiji, Wallis Islands and West Samoa (the name changed to Samoa later).
Supra-arcade downflows
Supra-arcade downflows (SADs) are sunward-traveling plasma voids that are sometimes observed in the Sun’s outer atmosphere, or corona, during solar flares. In solar physics, an “arcade” refers to a bundle of coronal loops, and the prefix “supra” indicates that the downflows appear above flare arcades. They were first described in 1999 using the Soft X-ray Telescope (SXT) on board the Yohkoh satellite. SADs are byproducts of the magnetic reconnection process that drives solar flares, but their precise cause remains unknown.
Solar eclipse of June 10, 2002
An annular solar eclipse occurred on June 10, 2002. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible in Indonesia, Palau (Kayangel Atoll), Northern Mariana and the western tip of Jalisco, Mexico.
Bastille Day event
The Bastille Day Flare or Bastille Day Event was a powerful solar flare on July 14, 2000, the national day of France, occurring near the peak of the solar maximum in solar cycle 23. The X5.7-class flare originated from a sunspot known as Active region 9077, which subsequently caused an S3 radiation storm on Earth fifteen minutes later as energetic protons bombarded the ionosphere. It was the biggest solar radiation event since 1989. The proton event was four times more intense than any previously recorded since the launches of SOHO in 1995 and ACE in 1997. The flare was also followed by a full-halo coronal mass ejection and a geomagnetic super storm on July 15–16. The geomagnetic storm peaked at the extreme level, G5, in the late hours of July 15.
Superflare
Solar superflares would have drastic effects, especially if they occurred as multiple events. Since they can occur on stars of the same age, mass and composition as the Sun this cannot be ruled out. However, solar-type superflare stars are very rare and are magnetically much more active than the Sun; if solar superflares do occur, it may be in well-defined episodes that occupy a small fraction of its time.
Solar eclipse of January 4, 2011
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A partial solar eclipse occurs in the polar regions of the Earth when the center of the Moon's shadow misses the Earth.
This was the first of four partial solar eclipses in 2011, with the others occurring on June 1, 2011, July 1, 2011, and November 25, 2011.
Solar eclipse of April 18, 1977
An annular solar eclipse took place on Monday, April 18, 1977. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible in South West Africa (today's Namibia), Angola, Zambia, southeastern Zaire (today's Democratic Republic of Congo), northern Malawi, Tanzania, Seychelles and the whole British Indian Ocean Territory.
Superflare
The high accuracy, the large number of stars observed and the long period of observation make Kepler ideal for detecting superflares. Studies published in 2012 and 2013 involved 83,000 stars over a period of 500 days (much of the data analysis was carried out with the help of five first-year undergraduates). The stars were selected from the Kepler Input Catalog to have T, the effective temperature, between 5100 and 6000K (the solar value is 5750K) to find stars of similar spectral class to the Sun, and the surface gravity log g > 4.0 to eliminate sub-giants and giants. The spectral classes range from F8 to G8. The integration time was 30 min in the original study. 1547 superflares were found on 279 solar-type stars.The most intense events increased the brightness of the stars by 30% and had an energy of 10 ergs. White-light flares on the Sun change the brightness by about 0.01%, and the strongest flares have a visible-light energy of about 10 ergs. (All energies quoted are in the optical bandpass and so are lower limits since some energy is emitted at other wavelengths.) Most events were much less energetic than this: flare amplitudes below 0.1% of the stellar value and energies of 2 × 10 ergs were detectable with the 30 minute integration. The flares had a rapid rise followed by an exponential decay on a time scale of 1–3 hours. The most powerful events corresponded to energies ten thousand greater than the largest flares observed on the Sun. Some stars flared very frequently: one star showed 57 events in 500 days, a rate of one every nine days. For the statistics of flares, the number of flares decreased with energy E roughly as E, a similar behaviour to solar flares. The duration of the flare increased with its energy, again in accordance with the solar behaviour.
Solar eclipse of July 14, 1749
An annular solar eclipse occurred on July 14, 1749. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Astrophysical X-ray source
Solar flares usually follow the solar cycle. CORONAS-F was launched on July 31, 2001 to coincide with the 23rd solar cycle maximum.
The solar flare of October 29, 2003 apparently showed a significant degree of linear polarization (> 70% in channels E2 = 40-60 keV and E3 = 60-100 keV, but only about 50% in E1 = 20-40 keV) in hard X-rays, but other observations have generally only set upper limits.
Coronal loops form the basic structure of the lower corona and transition region of the Sun. These highly structured and elegant loops are a direct consequence of the twisted solar magnetic flux within the solar body. The population of coronal loops can be directly linked with the solar cycle, it is for this reason coronal loops are often found with sunspots at their footpoints. Coronal loops populate both active and quiet regions of the solar surface. The Yohkoh Soft X-ray Telescope (SXT) observed X-rays in the 0.25-4.0 keV range, resolving solar features to 2.5 arc seconds with a temporal resolution of 0.5–2 seconds. SXT was sensitive to plasma in the 2-4 MK temperature range, making it an ideal observational platform to compare with data collected from TRACE coronal loops radiating in the EUV wavelengths.
Hyder flare
As Hyder flares are notably rare, few occurrences have been recorded since their discovery, the first being on August 31, 2012, the second being on June 4, 2014. This solar flare occurred in the Southeastern Galactic quadrant. This flare spanned more than . It was recorded to have happened around 14:30 Coordinated Universal Time (UTC). After the flare took place, solar activity was low for 24 hours.
Solar eclipse of March 18, 1969
An annular solar eclipse occurred on Tuesday, March 18, 1969. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from part of Indonesia, and two atolls (Faraulep and Gaferut) in the Trust Territory of the Pacific Islands which belongs to the Federated States of Micronesia now.
Solar flare
Since the beginning of space exploration, telescopes have been sent to space, where they work at wavelengths shorter than UV, which are completely absorbed by the atmosphere, and where flares may be very bright. Since the 1970s, the GOES series of satellites observe the Sun in "soft" X-rays, and their observations became the "standard measure" of flares, diminishing the importance of the Hα classification. "Hard" X-rays were observed by many different instruments, the most important today being the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Nonetheless, UV observations are today the "stars" of solar imaging with their incredible fine details that reveal the complexity of the solar corona. Spacecraft may also bring radio detectors at extremely long wavelengths (as long as a few kilometers) that cannot propagate through the ionosphere.
The following spacecraft missions have flares as their main observation target.
Astronautical hygiene
These are injections of energetic electrons, protons, alpha particles into interplanetary space during solar flare eruptions. During periods of maximum solar activity, the frequency and intensity of solar flares will increase. The solar proton events generally occur only once or twice a solar cycle.
Solar eclipse of June 21, 2020
An annular solar eclipse will occur on June 21, 2020. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Solar eclipse of December 14, 1955
An annular solar eclipse occurred on December 14, 1955. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from French Equatorial Africa (the part now belonging to Chad), Libya, Anglo-Egyptian Sudan (the part now belonging to Sudan) including the capital city Khartoum, French Somaliland (today's Djibouti) including the capital Djibouti City, British Somaliland (today's Somaliland) including the capital city Hargeisa, the Trust Territory of Somaliland (today's Somalia), the Maldives, Andaman and Nicobar Islands, Burma, Thailand including the capital city Bangkok, Cambodia, Laos, North Vietnam and South Vietnam (now belonging to Vietnam), China, British Hong Kong, Taiwan, and Ryukyu Islands. It was the third central solar eclipse visible from Bangkok from 1948 to 1958, where it is rare for a large city to witness 4 central solar eclipses in just 10 years. This is the 20th member Solar Saros 141, and the last of first set of solar eclipses without a penumbral internal contact (without a penumbra northern limit), the next event is the 1973 Dec 24 event, which is the first of 19 solar eclipses with a penumbral internal contact (has penumbral northern and southern limits) until 2298 Jul 09.
Solar eclipse of March 6, 1905
An annular solar eclipse occurred on March 6, 1905. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from Heard Island and McDonald Islands (now an Australian external territory), Australia, New Caledonia, and New Hebrides (now Vanuatu).
Solar eclipse of January 4, 1992
An annular solar eclipse occurred on January 4–5, 1992. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible in the Federal States of Micronesia, Nauru, Kiribati, Baker Island, Palmyra Atoll, Kingman Reef, and southwestern California, including the southwestern part of Los Angeles.
Solar flare
During World War II, on February 25 and 26, 1942, British radar operators observed radiation that Stanley Hey interpreted as solar emission. Their discovery did not go public until the end of the conflict. The same year Southworth also observed the Sun in radio, but as with Hey, his observations were only known after 1945. In 1943 Grote Reber was the first to report radioastronomical observations of the Sun at 160 MHz. The fast development of radioastronomy revealed new peculiarities of the solar activity like "storms" and "bursts" related to the flares. Today ground-based radiotelescopes observe the Sun from c. 15 MHz up to 400 GHz.
Solar eclipse of June 20, 1955
A total solar eclipse occurred on June 20, 1955. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide.
With a maximum duration of 7 minutes 8 seconds, this is the longest solar eclipse of saros series 136, as well as the longest total solar eclipse since the 11th century, and until the 22nd century. Totality beginning over the Indian Ocean, British Seychelles (today's Seychelles) and Maldives, crossing Ceylon (name changed to Sri Lanka later) including the capital city Colombo, Andaman Islands, Burma, Thailand including the capital city Bangkok, Cambodia, Laos, South Vietnam (now belonging to Vietnam), Paracel Islands and Scarborough Shoal (near the greatest eclipse), moving across the Philippines including the capital city Manila, Kayangel Atoll in the Trust Territory of the Pacific Islands (now belonging to Palau), Nukumanu Islands in the Territory of Papua New Guinea (today's Papua New Guinea), towards northern Ontong Java Atoll in British Solomon Islands (today's Solomon Islands) ending over Southwestern Pacific Ocean. It was the second central solar eclipse visible from Bangkok from 1948 to 1958, where it is rare for a large city to witness 4 central solar eclipses in just 10 years.
Solar storm of August 1972
The August 4 flare which triggered the extreme solar particle event (SPE) around and intense geomagnetic storm on Earth was among the largest documented by science. This flare saturated the Solrad 9 X-ray sensor at approximately X5.3 but was estimated to be in the vicinity of X20, the threshold of the very rarely reached R5 on the NOAA radio blackout space weather scale. A radio burst of 76,000 sfu was measured at 1 GHz. This was an exceptionally long duration flare, generating X-ray emissions above background level for more than 16 hours. Rare emissions in the gamma ray (formula_1-ray) spectrum were detected for the first time, on both August 4 and August 7, by the Orbiting Solar Observatory (OSO 7). The broad spectrum electromagnetic emissions of the largest flare are estimated to total 1-5 x 10 ergs in energy released.
Solar eclipse of November 4, 2097
An annular solar eclipse will occur on November 4, 2097. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Coronal rain
Coronal rain is a phenomenon that occurs in the sun's corona. It occurs when hot plasma in the corona cools and condenses in strong magnetic fields, usually associated with regions that produce solar flares. The plasma is attracted to the magnetic fields where it condenses and slowly falls back to the solar surface.
Solar eclipse of July 24, 2074
An annular solar eclipse will occur on July 24, 2074. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Solar eclipse of April 10, 2089
An annular solar eclipse will occur on April 10, 2089. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Solar flare
The most powerful flare ever observed was the first one to be observed, on September 1, 1859, and was reported by British astronomer Richard Carrington and independently by an observer named Richard Hodgson. The event is named the Solar storm of 1859, or the "Carrington event". The flare was visible to a naked eye (in "white light"), and produced stunning auroras down to tropical latitudes such as Cuba or Hawaii, and set telegraph systems on fire. The flare left a trace in Greenland ice in the form of nitrates and beryllium-10, which allow its strength to be measured today. Cliver and Svalgaard reconstructed the effects of this flare and compared with other events of the last 150 years. In their words: "While the 1859 event has close rivals or superiors in each of the above categories of space weather activity, it is the only documented event of the last ∼150 years that appears at or near the top of all of the lists."
Thermosphere
The solar X-ray and extreme ultraviolet radiation (XUV) at wavelengths < 170 nm is almost completely absorbed within the thermosphere. This radiation causes the various ionospheric layers as well as a temperature increase at these heights (Figure 1).
While the solar visible light (380 to 780 nm) is nearly constant with a variability of not more than about 0.1% of the solar constant, the solar XUV radiation is highly variable in time and space. For instance, X-ray bursts associated with solar flares can dramatically increase their intensity over preflare levels by many orders of magnitude over a time span of tens of minutes. In the extreme ultraviolet, the Lyman α line at 121.6 nm represents an important source of ionization and dissociation at ionospheric D layer heights. During quiet periods of solar activity, it alone contains more energy than the rest of the XUV spectrum. Quasi-periodic changes of the order of 100% or greater, with periods of 27 days and 11 years, belong to the prominent variations of solar XUV radiation. However, irregular fluctuations over all time scales are present all the time. During low solar activity, about half of the total energy input into the thermosphere is thought to be solar XUV radiation. Evidently, that solar XUV energy input occurs only during daytime conditions, maximizing at the equator during equinox.
Solar storm of August 1972
The most significant detected solar flare activity occurred from August 2 to August 11. Most of the significant solar activity emanated from active sunspot region McMath 11976 (MR 11976; sunspot regions being clusters of sunspot pairs). McMath 11976 was extraordinarily magnetically complex but its size was large although not exceptional. McMath 11976 produced 67 solar flares (4 of these X-class) during the time it was facing Earth, from July 29 to August 11. It also produced multiple relatively rare white light flares over multiple days. The same active area was long-lived. It persisted through five solar rotation cycles, first receiving the designation as Region 11947 as it faced Earth, going unseen as it rotated the far side of the Sun, then returning Earthside as Region 11976, before cycling as Regions 12007, 12045, and 12088, respectively.
Solar eclipse of July 9, 1926
An annular solar eclipse occurred on July 9, 1926. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from the islands of Pulo Anna and Merir in South Pacific Mandate in Japan (now in Palau) and Wake Island on July 10th (Saturday), and Midway Atoll on July 9th (Friday).
Solar flare
The frequency of occurrence of solar flares varies, from several per day when the Sun is particularly "active" to less than one every week when the Sun is "quiet", following the 11-year cycle (the solar cycle). Large flares are less frequent than smaller ones.
Solar cycle 24
On August 9 at 0805 UT, sunspot 1263 produced a massive X6.9-class solar flare, the third X-flare of Solar Cycle 24 and the most powerful so far (as of May 2013). There was also a CME associated with this burst. Although the flare was not Earth-directed, radiation created waves of ionization in Earth's upper atmosphere, briefly disrupting communications at some VLF and HF radio frequencies. A R3-level (strong) radio blackout alert was issued. A proton event greater than 10 MeV (=million electron volts) ions and exceeding 10 pfu (=proton flux units) was also reported, so a S1-level solar radiation storm was also issued.
Solar cycle 24
A filament eruption occurred in late hours of September 27 resulted in a brief S1 (minor) radiation storm, alerted by NOAA in early hours of next day. The Earth-directed CME associated with this event affected our planet on September 30. Geomagnetic storm levels reached the G3 on October 1. The filament eruption was connected to a C3.7 flare occurred in the vicinity of sunspot 1577.
Solar activity decreased remarkably this month. 4 minor solar flares, below M2 levels, were registered in September 2012.
On October 8 and 9, the arrival of a CME unrelated to solar flares and emitted on October 5 caused disturbances in the horizontal component of the Earth's magnetic field. The planetary Kp-index reached level 6, so a G2 (moderate) geomagnetic storm was reported. 
The Sun released a M9.0 flare on October 20. This was followed three days after on October 23, by a very impulsive flare, peaking as an X1.8 class event at 3:17 a.m. UTC. 
Both flares came from active region 1598 located on the left side (east) of the sun, which had previously been the source of a number of weaker flares. The M9.0 burst occurred when the sunspot was not yet rotated onto the Earth-facing side of the solar disk. The NOAA categorized the radio blackout associated with the X1.8 event as an R3, on a scale from R1 to R5. This was the 7th and last X-class flare in 2012. There was no associated Earth-directed coronal mass ejection (CME).
Solar eclipse of June 11, 2067
An annular solar eclipse will occur on June 11, 2067. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Solar eclipse of July 20, 1944
An annular solar eclipse occurred on Thursday, July 20, 1944. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from British Uganda (today's Uganda), Anglo-Egyptian Sudan (the part now belonging to South Sudan), British Kenya (today's Kenya), Ethiopia, British Somaliland (today's Somalia), British Raj (the part now belonging to India), Burma, Thailand, French Indochina (the parts now belonging to Laos and Vietnam), Philippines, South Pacific Mandate in Japan (the part now belonging to Hatohobei, Palau) the Territory of New Guinea (now belonging to Papua New Guinea).
AP Columbae
AP Columbae belongs to the class of stars known as UV Ceti flare stars. These are young low mass stars, which are strong sources of X-ray radiation and experience frequent flares. The latter are much like Solar flares but are much brighter as compared to the star's quiescent luminosity—the brightness of AP Columbae can increase as much as 10 times during the largest flares.
Solar eclipse of July 12, 2056
An annular solar eclipse will occur on July 12, 2056. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Solar cycle
The solar cycle or solar magnetic activity cycle is the nearly periodic 11-year change in the Sun's activity (including changes in the levels of solar radiation and ejection of solar material) and appearance (changes in the number and size of sunspots, flares, and other manifestations).
Flare star
Most flare stars are dim red dwarfs, although recent research indicates that less massive brown dwarfs might also be capable of flaring. The more massive RS Canum Venaticorum variables (RS CVn) are also known to flare, but it is understood that these flares are induced by a companion star in a binary system which causes the magnetic field to become tangled. Additionally, nine stars similar to the Sun had also been seen to undergo flare events prior
to the flood of superflare data from the Kepler observatory.
It has been proposed that the mechanism for this is similar to that of the RS CVn variables in that the flares are being induced by a companion, namely an unseen Jupiter-like planet in a close orbit.
Solar phenomena
Solar storms are caused by disturbances on the Sun, most often coronal clouds associated with solar flare CMEs emanating from active sunspot regions, or less often from coronal holes. The Sun can produce intense geomagnetic and proton storms capable of causing power outages, disruption or communications blackouts (including GPS systems) and temporary/permanent disabling of satellites and other spaceborne technology. Solar storms may be hazardous to high-latitude, high-altitude aviation and to human spaceflight. Geomagnetic storms cause aurorae.
Geomagnetic storm
Seventeen major flares erupted on the Sun between 19 October and 5 November 2003, including perhaps the most intense flare ever measured on the GOES XRS sensor—a huge X28 flare, resulting in an extreme radio blackout, on 4 November. These flares were associated with CME events that caused three geomagnetic storms between 29 October and 2 November, during which the second and third storms were initiated before the previous storm period had fully recovered. The minimum Dst values were −151, −353 and −383 nT. Another storm in this sequence occurred on 4–5 November with a minimum Dst of −69 nT. The last geomagnetic storm was weaker than the preceding storms, because the active region on the Sun had rotated beyond the meridian where the central portion CME created during the flare event passed to the side of the Earth. The whole sequence became known as the Halloween Solar Storm. The Wide Area Augmentation System (WAAS) operated by the Federal Aviation Administration (FAA) was offline for approximately 30 hours due to the storm. The Japanese ADEOS-2 satellite was severely damaged and the operation of many other satellites were interrupted due to the storm.
Superflare
Spectroscopic studies of superflares allow their properties to be determined in more detail, in the hope of detecting the cause of the flares. The first studies were made using the high dispersion spectrograph on the Subaru telescope in Hawaii. Some 50 apparently solar-type stars, known from the Kepler observations to show superflare activity, have been examined in detail. Of these, only 16 showed evidence of being visual or spectroscopic binaries; these were excluded since close binaries are frequently active, while in the case of visual binaries there is the chance of activity taking place on the companion. Spectroscopy allows accurate determinations of the effective temperature, the surface gravity and the abundance of elements beyond helium ('metallicity'); most of the 34 single stars proved to be main sequence stars of spectral type G and similar composition to the Sun. Since properties such as temperature and surface gravity change over the lifetime of a star, stellar evolution theory allows an estimate of the age of a star: in most cases the age appeared to be above several hundred million years. This is important since very young stars are known to be much more active. Nine of the stars conformed to the narrower definition of solar-type given above, with temperatures greater than 5600K and rotation periods longer than 10 days; some had periods above 20 or even 30 days. Only five of the 34 could be described as fast rotators.
Solar phenomena
A solar flare is a sudden flash of brightness observed over the Sun's surface or the solar limb, which is interpreted as an energy release of up to 6 × 10 joules of energy (about a sixth of the total Sun's energy output each second or 160 billion megatons of TNT equivalent, over 25,000 times more energy than released from the impact of Comet Shoemaker–Levy 9 with Jupiter). They may be followed by a coronal mass ejection. The flare ejects clouds of electrons, ions and atoms through the corona into space. These clouds typically reach Earth a day or two after the event. Similar phenomena in other stars are known as stellar flares.
Solar eclipse of July 1, 2011
A partial solar eclipse occurred on July 1, 2011. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A partial solar eclipse occurs in the polar regions of the Earth when the center of the Moon's shadow misses the Earth.
This is the first solar eclipse of Saros series 156, only visible as a partial solar eclipse in a small area south of South Africa and north of Antarctica. At greatest eclipse, the magnitude was just 0.097. It is the first new saros series to begin since saros 155 began with the partial solar eclipse of June 17, 1928.
Solar phenomena
A solar proton event (SPE), or "proton storm", occurs when particles (mostly protons) emitted by the Sun become accelerated either close to the Sun during a flare or in interplanetary space by CME shocks. The events can include other nuclei such as helium ions and HZE ions. These particles cause multiple effects. They can penetrate the Earth's magnetic field and cause ionization in the ionosphere. The effect is similar to auroral events, except that protons rather than electrons are involved. Energetic protons are a significant radiation hazard to spacecraft and astronauts. Kim, Myung-Hee Y.; Wilson, John W.; Cucinotta, Francis A.; Simonsen, Lisa C.; Atwell, William; Badavi, Francis F.; Miller, Jack, NASA Johnson Space Center; Langley Research Center, May 1999. Energetic protons can reach Earth within 30 minutes of a major flare's peak.
Solar eclipse of January 15, 1991
An annular solar eclipse occurred on January 15–16, 1991. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Annularity was visible in southwestern West Australia, Tasmania, New Zealand and French Polynesia. It was visible over Australia as a partial solar eclipse at sunrise on January 16.
Solar flare
Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona). The plasma medium is heated to tens of millions of Kelvin, while electrons, protons, and heavier ions are accelerated to near the speed of light. Flares produce electromagnetic radiation across the electromagnetic spectrum at all wavelengths, from radio waves to gamma rays. Most of the energy is spread over frequencies outside the visual range and so the majority of the flares are not visible to the naked eye and must be observed with special instruments. Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior.
Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona. The same energy releases may produce coronal mass ejections (CMEs), although the relationship between CMEs and flares is still not well understood.
Koronas-Foton
On 5 July 2009, Koronas-Foton's TESIS telescope registered the most powerful solar outburst of the year so far, lasting 11 minutes, from 06:07 to 06:18 GMT. Solar X-ray pick intensity reached С2.7 in a 5-level scale used to classify solar flares. The last equally powerful outburst occurred on 25 March 2008.
Hyder flare
A Hyder flare is slow, large-scale brightening that occurs in the solar chromosphere. It resembles a large but feeble solar flare and is identifiable as the signature of the sudden disappearance of a  solar prominence (a "disparition brusque"). 
These events occur in the quiet Sun, away from the active regions or sunspot groups, and typically in the polar crown filament zone. 
Hyder flares have a two-ribbon morphology and can be faintly observed in chromospheric emission lines such as Hα or as enhanced absorption in He I 1083 nm line.
Solar storm of August 1972
Astronomers first reported unusual flares on August 2, later corroborated by orbiting spacecraft. On August 3, Pioneer 9 detected a shock wave and sudden increase in solar wind speed from approximately . A shockwave passed Pioneer 10, which was 2.2 AU from the Sun at the time. The greatly constricted magnetosphere caused many satellites to cross outside Earth's protective magnetic field, such boundary crossings into the magnetosheath lead to erratic space weather conditions and potentially destructive solar particle bombardment. The Intelsat IV F-2 communications satellite solar panel arrays power generation was degraded by 5%, about 2 years worth of wear. An on-orbit power failure ended the mission of a Defense Satellite Communications System (DSCS II) satellite. Disruptions of Defense Meteorological Satellite Program (DMSP) scanner electronics caused anomalous dots of light in the southern polar cap imagery.
Solar flare
Solar flares strongly influence the local space weather in the vicinity of the Earth. They can produce streams of highly energetic particles in the solar wind or stellar wind, known as a solar proton event. These particles can impact the Earth's magnetosphere (see main article at geomagnetic storm), and present radiation hazards to spacecraft and astronauts. Additionally, massive solar flares are sometimes accompanied by coronal mass ejections (CMEs) which can trigger geomagnetic storms that have been known to disable satellites and knock out terrestrial electric power grids for extended periods of time.
Health threat from cosmic rays
The solar cycle is an approximately 11-year period of varying solar activity including solar maximum where the solar wind is strongest and solar minimum where the solar wind is weakest. Galactic cosmic rays create a continuous radiation dose throughout the Solar System that increases during solar minimum and decreases during solar maximum (solar activity). The inner and outer radiation belts are two regions of trapped particles from the solar wind that are later accelerated by dynamic interaction with the Earth's magnetic field. While always high, the radiation dose in these belts can increase dramatically during geomagnetic storms and substorms. Solar proton events (SPEs) are bursts of energetic protons accelerated by the Sun. They occur relatively rarely and can produce extremely high radiation levels. Without thick shielding, SPEs are sufficiently strong to cause acute radiation poisoning and death.
Neutron monitor
Approximately 10-15 times per decade, the Sun emits particles of sufficient energy and intensity to raise radiation levels on Earth's surface. The official list of GLEs is kept by the International GLE database. The largest of these events, termed a "ground level enhancement" (GLE) was observed on February 23, 1956. The most recent GLE, (#72) occurred on September 10, 2017 as a result of an X-class flare and was measured on the surface of both the Earth (by Neutron Monitors) and Mars (by the Radiation Assessment Detector on the Mars Science Laboratory's Curiosity Rover).
Solar eclipse
The Moon's orbit intersects with the ecliptic at the two nodes that are 180 degrees apart. Therefore, the new moon occurs close to the nodes at two periods of the year approximately six months (173.3 days) apart, known as eclipse seasons, and there will always be at least one solar eclipse during these periods. Sometimes the new moon occurs close enough to a node during two consecutive months to eclipse the Sun on both occasions in two partial eclipses. This means that, in any given year, there will always be at least two solar eclipses, and there can be as many as five.
Superflare
However, this does not match the known properties of superflare stars. Such stars are extremely rare in the Kepler data; one study showed only 279 such stars in 31,457 studied, a proportion below 1%; for older stars this fell to 0.25%. Also, about half of the stars which were active showed repeating flares: one had as many as 57 events in 500 days. Concentrating on solar-type stars, the most active averaged one flare every 100 days; the frequency of superﬂare occurrence in the most active Sun-like stars is 1000 times larger than that of the general average for such stars. This suggests that such behaviour is not present throughout a star's lifetime, but is confined to episodes of extraordinary activity. This is also suggested by the clear relation between the magnetic activity of a star and its superflare activity; in particular, superflare stars are much more active (based on starspot area) than the Sun.
Solar eclipse of February 5, 2065
A partial solar eclipse will occur on February 5, 2065. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A partial solar eclipse occurs in the polar regions of the Earth when the center of the Moon's shadow misses the Earth.
Solar cycle 23
Another major aurora display was observed on 1 April 2001, due to a coronal mass ejection hitting the Earth's magnetosphere. Auroras were observed as far south as Mexico and South Europe. A large solar flare (the second-most powerful ever recorded) occurred on 2 April 2001, an X20-class, but the blast was directed away from Earth.
Solar cycle 24
After releasing up to nine M-class flares in only one day, the active region 1429 erupted a powerful X5.4-class flare at 00:24 UTC the March 7. The related CME impacted the Earth on March 8, causing a G3 (strong) geomagnetic storm. This event marked the second strongest solar flare of Cycle 24 in terms of X-ray flux. NOAA launched a R3 (strong) radio blackout and a S3 (strong) solar radiation storm alerts. Just one hour after that first flare, nearby sunspot 1430 released a less powerful X1.3-class one. No coronal mass ejection (CME) associated to this event was reported. Months later, in June, NASA reported that its Fermi Gamma-ray Space Telescope detected in this powerful flare the highest flux of gamma rays—greater than 100 MeV—ever associated with an eruption on the Sun.
Solar eclipse of August 22, 1979
An annular solar eclipse occurred on August 22, 1979. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
Barnard's Star
In 1998 a stellar flare on Barnard's Star was detected based on changes in the spectral emissions on 17 July during an unrelated search for variations in the proper motion. Four years passed before the flare was fully analyzed, at which point it was suggested that the flare's temperature was 8000 K, more than twice the normal temperature of the star. Given the essentially random nature of flares, Diane Paulson, one of the authors of that study, noted that "the star would be fantastic for amateurs to observe".
The flare was surprising because intense stellar activity is not expected in stars of such age. Flares are not completely understood, but are believed to be caused by strong magnetic fields, which suppress plasma convection and lead to sudden outbursts: strong magnetic fields occur in rapidly rotating stars, while old stars tend to rotate slowly. For Barnard's Star to undergo an event of such magnitude is thus presumed to be a rarity. Research on the star's periodicity, or changes in stellar activity over a given timescale, also suggest it ought to be quiescent; 1998 research showed weak evidence for periodic variation in the star's brightness, noting only one possible starspot over 130 days.
Solar phenomena
Many solar phenomena change periodically over an average interval of about 11 years. This solar cycle affects solar irradiation and influences space weather, terrestrial weather and climate.
Solar maximum
Large solar flares often occur during a maximum. For example, the solar storm of 1859 struck the Earth with such intensity that the northern lights were visible as far from the poles as Cuba and Hawaii.
Solar Saros 147
Solar Saros 147, repeats every 18 years, 11 and 1/3 days, and contains 80 events in which 40 will be partial eclipses and 40 will be annular. There are no total or hybrid eclipses in this series. It includes 25 central solar eclipses with a penumbral internal contact (penumbra northern and southern limits), starting in 2129 and ending in 2562. Lunar Saros 140 interleaves with this solar saros with an event occurring every 9 years 5 days alternating between each saros series.
Solar flare
A solar flare is a sudden flash of increased brightness on the Sun, usually observed near its surface
and in close proximity to a sunspot group. 
Powerful flares are often, but not always, accompanied by a coronal mass ejection. Even the most powerful flares are barely detectable in the total solar irradiance (the "solar constant").
Sudden ionospheric disturbance
When a solar flare occurs on the Sun a blast of intense ultraviolet (UV) and x-ray (sometimes even gamma ray) radiation hits the dayside of the Earth after a propagation time of about 8 minutes. This high energy radiation is absorbed by atmospheric particles, raising them to excited states and knocking electrons free in the process of photoionization. The low altitude ionospheric layers (D region and E region) immediately increase in density over the entire dayside. The ionospheric disturbance enhances VLF radio propagation. Scientists on the ground can use this enhancement to detect solar flares; by monitoring the signal strength of a distant VLF transmitter, sudden ionospheric disturbances (SIDs) are recorded and indicate when solar flares have taken place. The small geomagnetic effect in the lower ionosphere appears as a small hook on magnetic records and is therefore called "geomagnetic crochet effect" or "sudden field effect".
Solar storm of August 1972
The arrival time of the associated coronal mass ejection (CME) and its coronal cloud, 14.6 hours, remains the record shortest duration as of November 2018, indicating an exceptionally fast and typically geoeffective event (normal transit time is two to three days). A preceding series of solar flares and CMEs cleared the interplanetary medium of particles, enabling the rapid arrival in a process similar to the solar storm of 2012. Normalizing the transit times of other known extreme events to a standard 1 AU to account for the varying distance of the Earth from the Sun throughout the year, one study found the ultrafast August 4 flare to be an outlier to all other events, even compared to the great solar storm of 1859, the overall most extreme known solar storm which is also known as the "Carrington event". This corresponds to an ejecta speed of an estimated .
Solar phenomena
Solar flares strongly influence space weather near the Earth. They can produce streams of highly energetic particles in the solar wind, known as a solar proton event. These particles can impact the Earth's magnetosphere in the form of a geomagnetic storm and present radiation hazards to spacecraft and astronauts.
Solar observation
The first modern, and clearly described, accounts of a solar flare and coronal mass ejection occurred in 1859 and 1860 respectively. On 1 September 1859, Richard C. Carrington, while observing sunspots, saw patches of increasingly bright light within a group of sunspots, which then dimmed and moved across that area within a few minutes. This event, also reported by R. Hodgson, is a description of a solar flare. The widely viewed total solar eclipse on 18 July 1860 resulted in many drawings, depicting an anomalous feature that corresponds with modern CME observations.
Coronal mass ejection
Coronal mass ejections are often associated with other forms of solar activity, most notably:
The association of a CME with some of those phenomena is common but not fully understood. For example, CMEs and flares are normally closely related, but there was confusion about this point caused by the events originating beyond the limb. For such events no flare could be detected. Most weak flares do not have associated CMEs; most powerful ones do. Some CMEs occur without any flare-like manifestation, but these are the weaker and slower ones. It is now thought that CMEs and associated flares are caused by a common event (the CME peak acceleration and the flare impulsive phase generally coincide). In general, all of these events (including the CME) are thought to be the result of a large-scale restructuring of the magnetic field; the presence or absence of a CME during one of these restructures would reflect the coronal environment of the process (i.e., can the eruption be confined by overlying magnetic structure, or will it simply break through and enter the solar wind).
Solar eclipse of February 4, 1981
An annular solar eclipse occurred on February 4–5, 1981. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
It was visible in Australia, crossing over Tasmania and southern Stewart Island of New Zealand near sunrise on February 5th, and ended at sunset over western South America on February 4th.
Coronal mass ejection
On the Sun, magnetic reconnection may happen on solar arcades—a series of closely occurring loops of magnetic lines of force. These lines of force quickly reconnect into a low arcade of loops, leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy during this process causes the solar flare and ejects the CME. The helical magnetic field and the material that it contains may violently expand outwards forming a CME. This also explains why CMEs and solar flares typically erupt from what are known as the active regions on the Sun where magnetic fields are much stronger on average.
Solar eclipse of July 20, 1925
An annular solar eclipse occurred on July 20, 1925. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from northern part of Northland Region and the whole Kermadec Islands in New Zealand on July 21st (Tuesday), and Rapa Iti in French Polynesia on July 20th (Monday).
Solar eclipse of November 11, 1901
An annular solar eclipse occurred on November 11, 1901. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from the Italian island Sicily, the whole British Malta (now Malta), Ottoman Tripolitania (now Libya), Egypt, Ottoman Empire (parts now belonging to Cretan State in Greece, Israel, Jordan and Saudi Arabia), Emirate of Jabal Shammar (now belonging to Saudi Arabia), Aden Protectorate (now belonging to Yemen), Muscat and Oman (now Oman), British Raj (the parts now belonging to India, Andaman and Nicobar Islands and Myanmar), British Ceylon (now Sri Lanka), Siam (name changed to Thailand later), French Indochina (the parts now belonging to Cambodia, southern tip of Laos and southern Vietnam, including Phnom Penh), Bombay Reef in the Paracel Islands, and Philippines.
Solar flare
Flares produce radiation across the electromagnetic spectrum, although with different intensity. They are not very intense in visible light, but they can be very bright at particular atomic lines. They normally produce bremsstrahlung in X-rays and synchrotron radiation in radio.