The first panel of Fig. 1 shows an example of a peaked electron distribution. The time interval of the ELS spectrogram is 12 min, revealing a clear “inverted-V” structure over a 2-min interval at the centre of the spectrogram. The DEF energy spectrum at the right shows a positive gradient below the energy of the peak, which is at approximately 60 eV. This corresponds to a peak of similar energy when the energy spectrum is plotted in PSD, but is not shown here. By comparing the energy spectrum of the electron feature to those from the different regions around Mars we find the origin is most likely from the solar wind. Comparing to the modelled Maxwellian distributions show the presence of an accelerated peak as well as an added contribution of heated electrons. This indicates the electron feature could be some way between penetrating solar wind and magnetosheath electrons. Evidence of electrons being accelerated and heated has been found in previous analysis of “inverted-V” electrons and is observed as preferably transverse to the magnetic field at low altitudes (Lundin et al., 2006b; Dubinin et al., 2009).
ELS spectrogram
time interval
12 min
min
clear “inverted-V” structure
over
2-min
min
peak
energy
approximately 60 eV.
eV