HR: 15:25h
AN: P33C-08    [Abstracts]
TI: Solar control of the Martian Ionosphere as Detected by MARSIS Active Ionospheric Sounder
AU: * Morgan, D D
EM: david-morgan@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242, United States
AU: Gurnett, D A
EM: donald-gurnett@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242, United States
AU: Kirchner, D L
EM: donald-kirchner@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242, United States
AU: Fox, J L
EM: jane.fox@wright.edu
AF: Wright State University, Department of Physics, Dayton, OH 45435, United States
AU: Nielsen, E
EM: nielsen@mps.mpg.de
AF: Max Plank Institute for Aeronomy, Max Plank Str 2, Katlenburg-Lindau, D-37191, Germany
AU: Plaut, J J
EM: plaut@mail.jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak grove Dr., Pasadena, CA 91109, United States
AU: Picardi, G
EM: picar@infocom.uniroma1.it
AF: "La Sapienza" The University of Rome, INFOCOM Department, Rome, 00184, Italy
AB: The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), aboard the ESA spacecraft Mars Express, was deployed 17 June 2005 and commissioned in July 2005. MARSIS includes an Active Ionospheric Sounding (AIS) mode, which targets the topside ionosphere of Mars. Between August 2005 and July 2007, the spacecraft performed approximately 2500 orbits. From these orbits we have selected for analysis some 30,000 ionograms, about one-half of which were acceptable for inversion to an electron density profile. We bin these data by various quantities and plot the peak plasma densities and their corresponding altitudes from each bin as a function of solar zenith angle. Each plot can then be fit to a Chapman model to determine characteristic values of the subsolar plasma density peak, subsolar density peak altitude, and neutral scale height for that bin. The results from each bin can then be plotted as a function of the binned quantity to infer trends in the martian ionosphere. We detect an increase in electron density in the martian ionosphere with solar activity as indexed by F10.7 flux and XUV flux from SORCE XPS, both corrected for the changing distance of Mars from the Sun. We see an average change of about 6% in the subsolar peak electron density and a 6 km increase in the subsolar peak density altitude during periods when we can infer the presence of solar energetic particles from MARSIS AIS surface reflection data. We also see variation in the Chapman parameters due to seasonal and areodetic variation. In particular, at high latitudes near the summer solstice in both northern and southern hemispheres, we note an increase in the neutral scale height and decrease in the electron density peak altitude.
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2459 Planetary ionospheres (5435, 5729, 6026)
DE: 2479 Solar radiation and cosmic ray effects
DE: 2481 Topside ionosphere
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting