HR: 0800h
AN: P41A-0198    [Abstracts]
TI: Electron Densities in the Upper Ionosphere of Mars from the Excitation of Local Electron Plasma Oscillations
AU: * Duru, F
EM: firdevs-duru@uiowa.edu
AF: The University of Iowa, Dept. of Physics and Astronomy, The University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242, United States
AU: Gurnett, D A
EM: donald-gurnett@uiowa.edu
AF: The University of Iowa, Dept. of Physics and Astronomy, The University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242, United States
AU: Morgan, D D
EM: david-morgan@uiowa.edu
AF: The University of Iowa, Dept. of Physics and Astronomy, The University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242, United States
AU: Modolo, R
EM: modolo@irfu.se
AF: The University of Iowa, Dept. of Physics and Astronomy, The University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242, United States
AU: Nagy, A F
EM: anagy@umich.edu
AF: The University of Michigan, Dept. of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109-2143, United States
AU: Najib, D
EM: dnajib@umich.edu
AF: The University of Michigan, Dept. of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109-2143, United States
AU: Plaut, J J
EM: Jeffrey.J.Plaut@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Picardi, G
EM: picar@infocom.uniromal.it
AF: La Sapienza University of Rome, Infocom Department, "La Sapienza" University of Rome, Rome, 00184, Italy
AB: In addition to the remote sounding of the ionosphere, the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on the Mars Express spacecraft, also excites local electron plasma oscillations. This paper summarizes the investigation of the local electron density using measurements of the locally excited electron plasma oscillation frequency. One of the advantages of this method is that the electron densities can be measured at very high altitudes, where remote ionospheric echoes cannot be detected. Measurements from 503 orbits over the period from August 4, 2005 to July 31, 2007 show that the average electron densities at a given solar zenith angle (SZA) decrease exponentially with increasing altitude. There is considerable variability at a given altitude due to the fact that the data at a specific altitude are obtained from different orbits. On the dayside of Mars, this exponential behavior continues up to altitudes of around 750 km. The scale height, in this altitude region, ranges between 130 km and 190 km. The average electron density is almost constant throughout the dayside in a given altitude range, but decreases rapidly as the spacecraft goes into the nightside. Simulations performed using different methods, show that the nearly constant density at a given altitude is due to transport effects. Investigation of individual orbits shows that the electron density throughout a pass often has large fluctuations, sometimes as much as ∆ne/ne ~ 50 %, on time scales as small as 8 s.
DE: 2437 Ionospheric dynamics
DE: 2439 Ionospheric irregularities
DE: 2459 Planetary ionospheres (5435, 5729, 6026)
DE: 2481 Topside ionosphere
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting