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MGS Radio Science Electron Density Profiles: Interannual Variability and Implications for the Martian Neutral AtmosphereMartian electron density profiles provided by the Mars Global Surveyor (MGS) Radio Science (RS) experiment over the 95-200 km altitude range indicate that the height of the electron peak and the longitudinal structure of the peak height are sensitive indicators of the physical state of the Mars lower atmosphere. The present analysis is carried out on five sets of occultation profiles, all at high solar zenith angles (SZA). Variations spanning 2-Martian years are investigated near aphelion conditions at high Northern latitudes (64.7-77.6N). A mean ionospheric peak height of 133.5-135 km was obtained for all aphelion profiles near SZA = 78-82; a corresponding mean peak density of 7.3-8.5 x 10(exp 4)/cu cm was also measured, reflecting solar moderate conditions. Strong wave 2-3 oscillations in peak heights were observed as a function of longitude over both Martian seasons. The Mars Thermospheric General Circulation Model (MTGCM) is exercised for Mars aphelion conditions. The measured interannual variations in the mean and longitude structure of the peak heights are small (consistent with MTGCM simulations), signifying the repeatability of the Mars atmosphere during aphelion conditions. A non-migrating (semi-diurnal period, wave#l eastward propagating) tidal mode is likely responsible for the wave#3 longitude features identified. The height of this photochemically driven peak can be observed to provide an ongoing monitor of the changing state of the Mars lower atmosphere. The magnitudes of these same peaks may reflect more than changing solar EUV fluxes when they are located in the vicinity of Mars crustal magnetic field centers.
Document ID
20030063132
Acquisition Source
Headquarters
Document Type
Preprint (Draft being sent to journal)
Authors
Bougher, Stephen W.
(Michigan Univ. Ann Arbor, MI, United States)
Engel, S.
(Arizona Univ. Tucson, AZ, United States)
Hinson, D. P.
(Stanford Univ. Stanford, CA, United States)
Murphy, J. R.
(New Mexico State Univ. Las Cruces, NM, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Astronomy
Funding Number(s)
CONTRACT_GRANT: NAG5-12442
Distribution Limits
Public
Copyright
Other

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