HR: 1340h
AN: P13A-0136    [Abstracts]
TI: Probing upper thermospheric neutral densities at Mars using electron reflectometry
AU: * Engel, J H
EM: jesse.engel@gmail.com
AF: UC Berkeley Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Lillis, R J
EM: rlillis@ssl.berkeley.edu
AF: UC Berkeley Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Lillis, R J
EM: rlillis@ssl.berkeley.edu
AF: UC Berkeley Physics Department, 366 Leconte Hall #7300, Berkeley, CA 94720-7300 United States
AU: Mitchell, D L
EM: dmitchell@ssl.berkeley.edu
AF: UC Berkeley Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Brain, D A
EM: brain@ssl.berkeley.edu
AF: UC Berkeley Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Lin, R P
EM: rlin@ssl.berkeley.edu
AF: UC Berkeley Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Lin, R P
EM: rlin@ssl.berkeley.edu
AF: UC Berkeley Physics Department, 366 Leconte Hall #7300, Berkeley, CA 94720-7300 United States
AU: Bougher, S W
EM: bougher@umich.edu
AF: University of Michigan Space Physics Research Laboratory, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Acuna, M H
EM: mario.acuna@gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, NASA, Greenbelt, MD 20771 United States
AB: 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 (~150 - 200km altitude) densities at 2am local time, continuously from 1999 to 2005 in regions where crustal fields exist, approximately 40 percent of the planet. We find a mean density of 0.028kg/km3 at 160km and observe a latitude-dependent, repeatable seasonal variation of up to a factor of 4, with inter-annual differences and consistently lower winter densities at high latitudes, compared with the tropics (0° - 25°). The mean densities and overall seasonal variation are in general agreement with the Mars Thermosphere Global Circulation Model (MTGCM), while the specific latitude dependence is not. These measurements are important for improved understanding of the dynamics of Mars' upper atmosphere and for planning spacecraft aerobraking maneuvers.
DE: 5400 PLANETARY SCIENCES: SOLID SURFACE PLANETS
DE: 5405 Atmospheres (0343, 1060)
DE: 5421 Interactions with particles and fields
DE: 5440 Magnetic fields and magnetism
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005