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withers

HR: 0800h
AN: SM41B-1868 Poster
TI: Total Electron Content in the Mars Ionosphere: temporal studies and dependence on solar inputs and crustal magnetic fields
AU: Jolitz, R
EM: rjolitz@berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, Los Gatos, CA, USA
AU: *Brain, D A
EM: brain@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, Los Gatos, CA, USA
AU: Lillis, R J
EM: rlillis@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, Los Gatos, CA, USA
AU: Fillingim, M O
EM: matt@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, Los Gatos, CA, USA
AU: Withers, P
EM: withers@bu.edu
AF: Center for Space Physics, Boston University, Boston, MA, USA
AU: England, S
EM: england@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, Los Gatos, CA, USA
AU: Safaeinili, A
EM: ali.safaeinili@jpl.nasa.gov
AF: Jet Propulsion Laboratory, Pasadena, CA, USA
AB: Total Electron Content (TEC) derived from radar signal distortions is a useful tool in probing the ionosphere of Mars. We consider 26 months of data from the subsurface mode of the Mars Express MARSIS instrument and confirm that the TEC dependence on solar zenith angle (SZA) approximately matches Chapman theory. After detrending this dependence, we find no clear trend with Martian season or dust activity but find that disturbed solar and space weather conditions can produce prolonged higher TEC values and that isolated solar energetic particle events are coincident with short-lived increases in TEC of ~1015 m-2 at all SZAs. We present the first comparison between TEC and directly-measured solar EUV flux in the 30.4 nm He-II line. We find that the relationship between TEC and both He-II line irradiance and F10.7 solar radio flux (a long-used EUV proxy) can be expressed as power laws with exponents of 0.54 and 0.44 respectively, in approximate agreement with Chapman theory. We also present statistical correlation studies comparing TEC with solar wind and solar energetic particle proxies. Last, we compare TEC with the elevation angle and topology of crustal magnetic field. We find that, on the night side, TEC values are noticeably higher in regions where this topology gives solar wind electrons direct access to the Martian atmosphere.



a) plots TEC from all data as a function of SZA and overlays TEC curves corresponding to 4 periods of interest. Panels b-f are timeseries. b) shows normalized TEC in different ranges of solar zenith angle. c) plots normalized proxies for solar energetic particle flux (see text). d) is identical to panel b) but with the curves offset for clarity. e) simultaneously plots 0.1-0.8 nm solar x-ray irradiance from the Earth-orbiting GOES 12 satellite and the Earth-Mars angular separation. f) simultaneously plots solar EUV irradiance in the 30.4 nm He-II line as measured by the TIMED-SEE instrument (scaled and phase-shifted from Earth to Mars) and globally-averaged Martian dust opacity as measured by the THEMIS instrument (the discontinuous line results from data gaps).

DE: [2455] IONOSPHERE / Particle precipitation
DE: [2459] IONOSPHERE / Planetary ionospheres
SC: SPA-Magnetospheric Physics (SM)
MN: 2010 Fall Meeting