Open AccessVariation of the Martian ionospheric electron density from Mars Express radar soundings
Author(s) -
Morgan D. D.,
Gurnett D. A.,
Kirchner D. L.,
Fox J. L.,
Nielsen E.,
Plaut J. J.
Publication year - 2008
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008ja013313
Subject(s) - ionosphere , solar zenith angle , martian , mars exploration program , atmospheric sciences , zenith , electron density , altitude (triangle) , solar maximum , scale height , latitude , atmosphere of mars , thermosphere , physics , environmental science , solar cycle , meteorology , solar wind , geophysics , electron , astronomy , optics , plasma , geometry , mathematics , quantum mechanics
The Mars Advanced Radar for Subsurface and Ionospheric Sounding aboard Mars Express has been in operation for over 2 years. Between 14 August 2005 and 31 July 2007, we obtain 34,492 ionospheric traces, of which 14,060 yield electron density profiles and 12,291 yield acceptable fits to the Chapman ionospheric model. These results are used to study the Martian ionosphere under changing conditions: the presence or absence of solar energetic particles, solar EUV flux, season, solar zenith angle, and latitude. The 2‐year average subsolar maximum electron density n 0 is 1.62 × 10 5 cm −3 , the average subsolar electron density altitude h 0 is 128.2 km, and the average neutral scale height H is 12.9 km. Solar energetic particle events are associated with a 6% increase in n 0 , a 3 km decrease in h 0 , and a 0–7 km decrease in H . The value of n 0 varies smoothly between 1.4 × 10 5 and 1.8 × 10 5 cm −3 , yielding d ln n 0 / d ln F10.7 = 0.30 ± 0.4; h 0 varies between 115 and 135 km, while H remains relatively constant with EUV flux and season, in contrast with previous work. The value of h 0 decreases toward the terminator at low latitude but increases poleward during summer; H varies from 11 km, for solar zenith angle less than 40°, to between 14 and 17 km near the terminator, depending on season. Near‐peak temperatures vary between 220 K and 300 K, less variation than indicated by modeling, probably due to sampling near solar minimum.