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withers

HR: 1140h
AN: P52A-09
TI: Modeling Mars’ Ionosphere with Constraints from Same-Day Observations by Mars Global Surveyor and Mars Express
AU: *Lollo, A
EM: alollo@bu.edu
AF: Boston University, Brookline, MA, USA
AU: Mendillo, M
EM: mendillo@bu.edu
AF: Boston University, Brookline, MA, USA
AU: Withers, P
EM: withers@bu.edu
AF: Boston University, Brookline, MA, USA
AU: Matta, M
EM: majdm@bu.edu
AF: Boston University, Brookline, MA, USA
AU: Paetzold, M
EM: mpaetzol@uni-koeln.de
AF: University of Cologne, Cologne, Germany
AU: Tellmann, S
EM: silvia.tellmann@uni-koeln.de
AF: University of Cologne, Cologne, Germany
AB: We have analyzed a brief period of same-day observations of the Martian ionosphere using data obtained in December 2004 from the Mars Global Surveyor (MGS) and Mars Express (MEX) radio occultation experiments. During the overlap period, the MGS occultations occur at high latitudes in the northern hemisphere, under summer solstice conditions (Ls=125-139 degrees), and at early local times in the Martian day while the MEX occultations all pertain to the southern hemisphere (winter solstice), span lower to upper mid-latitudes, and again occur early in the local time day at Mars. We developed several versions of a 1-dimensional model in an attempt to simulate more successfully the altitudes and peak electron densities of the two photo-chemical layers (M1 and M2) obtained during the joint MGS-MEX observing period. Four basic processes are examined: (1) modification to a model neutral atmosphere, (2) departures from thermal equilibrium between plasma and neutrals, (3) modifications to solar irradiance input, and (4) methods of handling secondary ionization. None of these single-parameter-space simulation experiments produce a definitive solution without raising questions about basic behavior. Our final simulation uses a modified neutral atmosphere to correct layer heights at the MGS and MEX observing sites, together with an electron temperature adjustment to chemistry in order to improve predicted M2 peak electron density, and a secondary ionization adjustment, as a function of solar zenith angle, needed to improve predicted M1 peak electron density.
DE: [6225] PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Mars
SC: Planetary Sciences (P)
MN: 2010 Fall Meeting