Upper Ionosphere of Mars During Solar Quiet and Disturbed Conditions - Planetary Exploration and Science: Recent Results and Advances - page 132

Fig. 7.12 Electron density profile predicted for 29 September 1989 SEP event, neglecting
photoionisation ( grey solid line ) and including photoionisation ( black solid line ). These two
profiles are identical below 100 km. The black dashed line shows the electron density profile from
generalised model (Reproduced from Sheel et al. ( 2012 ) by permission of John Wiley & Sons Ltd.)
auroral events ASPERA-3 measured an increase in the electron flux by an order of
magnitude. Before and after this event, the electron flux decreased by two orders of
magnitude. Leblanc et al. too found a broader peak in TEC during the SPICAM
measurements of an auroral event. This suggests that electron density increased
significantly in the auroral ionosphere of Mars during this event. Figure 7.14a-g
displays the measurements by SPICAM (Fig. 7.14g ), MGS/Electron Reflectometer
(ER) (Fig. 7.14f ), ASPERA-3 (Figs. 7.14d, e ), MARSIS (Fig. 7.14c )andtheMEX
altitude (Fig. 7.14a ) and MEX latitude (Fig. 7.14b ). MEX observations were carried
out on 26 January 2006 during orbit # 2621. Track of MEX during this orbit was
at local time of 20:30 h at a longitude of 180 ı that is above the most intense
crustal magnetic field recorded by MGS (Mitchell et al. 2007 ;Haideretal. 2010 ).
SPICAM observed a significant increase of auroral light between 14:04:01 UT and
14:04:15 UT.
It is found that the energy distribution of the downward electron flux measured
by ASPERA-3 exhibited non-Maxwellian features similar to those observed in the
V-shaped potential structure of Earth's auroral zone (cf. Fang et al. 2010 ; Lei and
Zhang 2009 ; Lillis et al. 2009 ; Fillingim et al. 2010 ; Lundin et al. 2011 ). Ip ( 2012 )
proposed a mechanism for the acceleration of ions and electrons in the Martian
auroral zone. Figure 7.15 represents a schematic view of inverted V-shaped potential
structures, where electrons are precipitating downward and conic ions are escaping
upward in the presence of strong crustal magnetic fields. Ip suggested that only those
ions, which are created in the crustal fields connected to the interplanetary magnetic
fields, would be able to escape. The ions which are created in the magnetic flux
tubes of closed field lines will be trapped in a bouncing motion. The southern aurora
may not be visible to the human eyes because they were observed in the ultraviolet
wavelength region.