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Mendillo, Michael, Lollo, Anthony, Withers, Paul, Matta, Majd, Paetzold, Martin and Tellmann, Silvia (2011). Modeling Mars' ionosphere with constraints from same-day observations by Mars Global Surveyor and Mars Express. J. Geophys. Res-Space Phys., 116. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-9402

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Abstract

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. These data were taken shortly after sunrise under solstice conditions in both hemispheres, with MGS in the summer (northern) hemisphere at high latitudes while MEX was in the winter (southern) hemisphere at midlatitudes. Such two-satellite, dual-hemisphere data sets are unique for the modern era of ionospheric observations at Mars and provide good test cases for constraints of key parameters commonly used in models of the Martian ionosphere. Several iterations of a 1-dimensional model are developed in attempts to simulate more successfully the altitudes, absolute magnitudes and shapes of the two photo-chemical layers (M1 and M2) obtained during the joint MGS-MEX observing period. Three basic processes are examined: (1) selection of the optimal model neutral atmospheres, (2) the effects due to departures from thermal equilibrium between electrons, ions and neutrals, (3) methods of handling secondary ionization. While general circulation models fully coupled to plasma transport codes are required for global simulations of the full system, the computational complexity and computer resources needed often result in the use of parameterizations relating electron and ion temperatures to neutral temperatures and secondary ionization to primary photo-ionization profiles. Here we develop such schemes and test them within the framework of same day observations in both hemispheres. The occurrence of same day, separate hemisphere, radio occultation profiles is important because the solar irradiance has to be held constant for modeling both sites, and thus this is the first study of this kind to be done. The overall results stress the dominant influence of solar zenith angle effects on production for the M2-layer via primary solar ionization, its augmentation by similar to 30% due to secondary ionization, and further enhancements due to reduced chemical loss when the electron temperature exceeds the neutral temperature. Secondary ionization is the most crucial process for the M1-layer. The influence of very different crustal magnetic field morphologies at the two observing locations did not seem to be a crucial source of differentiation for processes that control the average values of the peak electron densities of the two photo-chemical layers.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Mendillo, Michael UNSPECIFIED UNSPECIFIED UNSPECIFIED Lollo, Anthony UNSPECIFIED UNSPECIFIED UNSPECIFIED Withers, Paul UNSPECIFIED UNSPECIFIED UNSPECIFIED Matta, Majd UNSPECIFIED UNSPECIFIED UNSPECIFIED Paetzold, Martin UNSPECIFIED UNSPECIFIED UNSPECIFIED Tellmann, Silvia UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-485594
DOI:	10.1029/2011JA016865
Journal or Publication Title:	J. Geophys. Res-Space Phys.
Volume:	116
Date:	2011
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-9402
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RADIO OCCULTATION MEASUREMENTS; ELECTRON-DENSITY PROFILES; MAGNETIC-FIELD; UPPER-ATMOSPHERE; NEUTRAL ATMOSPHERE; MARTIAN IONOSPHERE; ANALYTIC FITS; VARIABILITY; EVOLUTION; ATOMS Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/48559