Upper Ionosphere of Mars During Solar Quiet and Disturbed Conditions - Planetary Exploration and Science: Recent Results and Advances - page 136

1.4

1 TECU = 1x10 16 el / m 2

1.2

1.0

0.8

0.6

0.4

0.2

0.0

SSMIN
Perihelion

SSMIN
Aphelion

SSMAX
Aphelion

SSMAX
Perihelion

Fig. 7.16 Model results for noontime ionospheric TEC in the altitude range 100-200 km at
the subsolar latitude on Mars for aphelion/perihelion positions during solar maximum/minimum
conditions (Reproduced from Mendillo et al. ( 2004 ) by permission of John Wiley & Sons Ltd.)

conditions. It should be noted that TEC in the Earth's ionosphere is larger during
solar maximum conditions by one to two orders of magnitude (Rishbeth and
Mendillo 2004 ) not because of Earth's closer distance to the sun, but due to the
non-photochemical layer F2, providing major contribution to the TEC integral.
Thus, photochemical models in Mars' ionosphere exhibit minimum solar cycle
variations.
Using MARSIS data obtained from MEX, Lillis et al. ( 2010 ) have reported that
disturbed solar and space weather conditions can produce prolonged higher TEC
values, while an individual SEP event causes a short-lived absolute increase in TEC.
They also found a relationship between TEC and both He-II line irradiance and F 10.7
solar radio flux as power laws with exponents of 0.54 and 0.44, respectively. As
mentioned before, Haider et al. ( 2012 ) used radio occultation data of MGS at high
latitudes (65.3-65.6 ı N, 69.3-69.6 ı N and 74.6-77.5 ı N) and studied the effects of
solar X-ray flares on TEC in the E region of the Martian ionosphere. Modelling of
flare-induced solar X-ray fluxes, ion production rates, electron densities and TEC
were carried out for solar flare events that occurred on 29 and 31 May 2003 and 17
January and 13 May 2005. They found that solar X-ray flares caused enhancements
in the electron density by a factor of 5-6 during disturbed condition. The observed
and estimated electron density profiles for quiet and disturbed conditions are
represented in Fig. 7.17 for solar X-ray flare of 31 May 2003. It should be noted
that the measured electron density profile cannot be reproduced completely by this
model. This is due to the fact that while E and F layers in the Martian ionosphere at
90-110 km and 130-140 km are produced due to absorption of both solar X-ray