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withers

HR: 1340h
AN: SA13A-1879 Poster
TI: How Chapman-like is the ionosphere of Mars?
AU: *Girazian, Z R
EM: zrjg@bu.edu
AF: Center for Space Physics, Boston University, Boston, MA, USA
AU: Withers, P
EM: withers@bu.edu
AF: Center for Space Physics, Boston University, Boston, MA, USA
AU: Fallows, K
EM: kfallows@bu.edu
AF: Center for Space Physics, Boston University, Boston, MA, USA
AU: Paetzold, M
EM: mpaetzol@uni-koeln.de
AF: University of Cologne, Cologne, Germany
AU: Tellmann, S
EM: silvia.tellmann@uni-koeln.de
AF: University of Cologne, Cologne, Germany
AB: Many investigators have concluded that the main Martian ionospheric layer can, in many respects, be statistically described by Chapman theory. Here we investigate two predictions of this theory for the ionosphere of Mars using Mars Express radio occultation observations. Chapman theory predicts a precise functional form for the vertical structure of the ionosphere of Mars. Past investigations have inferred that this prediction is qualitatively satisfied but without rigorous and quantitative evaluation. Here we quantitatively determine how well the vertical structure of the main layer is represented by a Chapman layer shape. The second prediction from Chapman theory we investigate is how the peak electron density $N_m$ depends on the solar flux. In Chapman theory $N_m \propto F^{k}$ where $k = 0.5$ and $F$ is the monochromatic solar photon flux at the top of the atmosphere. Many past studies have used the $F_{10.7} $ or $E_{10.7}$ solar proxies and assumed that they are proportional to $F$. The best fit exponents have varied widely with $k \approx 0.35$, much less than the expected $k = 0.5$. The reason for non-Chapman $k$ values is either because the solar flux dependence of $N_m$ is not described well by Chapman theory or the $F_{10.7} $ and $E_{10.7}$ proxies may not be a good description of the ionizing solar flux for the ionosphere of Mars. In order to explore the latter option we use a different proxy for the solar flux $F$, the integrated photon flux from $ \lambda = 0.5$ to $90$ nm provided by the SOLAR2000 model. Finally, we report the results of our analysis and discuss their implications for the use of idealized Chapman theory in the ionosphere of Mars.
DE: [2400] IONOSPHERE
DE: [2459] IONOSPHERE / Planetary ionospheres
DE: [2499] IONOSPHERE / General or miscellaneous
SC: SPA-Aeronomy (SA)
MN: 2011 Fall Meeting