Title: Probing
upper thermospheric neutral densities at Mars using electron
reflectometry
Source: GEOPHYSICAL
RESEARCH LETTERS 32 (23): Art. No. L23204 DEC 15 2005
Document Type: Article
Language: English
Abstract: We
present a new technique for inferring neutral densities in the Martian
upper atmosphere from atmospheric absorption of magnetically reflected
solar wind electrons. Using electron loss cone measurements from the
Magnetometer/Electron Reflectometer (MAG/ER) experiment on board Mars
Global Surveyor (MGS), we derive upper thermospheric (similar to
160-230 km altitude) densities in the southern hemisphere from
160\degrees to 200 degrees E at 2am local time, continuously from 1999
to 2005. We find a mean density of 0.027 kg/km(3) at 160 km and observe
a latitude-dependent, repeatable seasonal variation of a factor of
1.8-4, with inter-annual differences and consistently lower winter
densities at 50 degrees-55 degrees S, compared with 0 degrees-30
degrees S. The mean densities, overall seasonal variation and latitude
dependence are in general agreement with the Mars Thermosphere Global
Circulation Model (MTGCM). These measurements are important for
improved understanding of the dynamics of Mars' upper atmosphere and
for planning spacecraft aerobraking maneuvers.
KeyWords Plus: CRUSTAL
MAGNETIC-FIELD
Addresses: Lillis
RJ (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA
94720 USA
Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA
Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA
Univ Michigan, Ann Arbor, MI 48109 USA
NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
Publisher: AMER
GEOPHYSICAL UNION, 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
Subject Category: GEOSCIENCES,
MULTIDISCIPLINARY
IDS Number: 998BJ
ISSN: 0094-8276
