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Ann. Geophys., 26, 77-86, 2008
www.ann-geophys.net/26/77/2008/
© European Geosciences Union 2008
Parameterization of ionization rate by auroral electron precipitation in Jupiter
Y. Hiraki1 and C. Tao2
1Graduate School of Energy Science, Kyoto University, Uji, Japan
2Department of Geophysics, Tohoku University, Sendai, Japan
Abstract. We simulate auroral electron precipitation into the Jovian atmosphere in
which electron multi-directional scattering and energy degradation processes
are treated exactly with a Monte Carlo technique. We make a parameterization
of the calculated ionization rate of the neutral gas by electron impact in a
similar way as used for the Earth's aurora. Our method allows the altitude
distribution of the ionization rate to be obtained as a function of an
arbitrary initial energy spectrum in the range of 1–200 keV. It also
includes incident angle dependence and an arbitrary density distribution of
molecular hydrogen. We show that there is little dependence of the estimated
ionospheric conductance on atomic species such as H and He. We compare our
results with those of recent studies with different electron transport
schemes by adapting our parameterization to their atmospheric conditions. We
discuss the intrinsic problem of their simplified assumption. The ionospheric
conductance, which is important for Jupiter's magnetosphere-ionosphere
coupling system, is estimated to vary by a factor depending on the electron
energy spectrum based on recent observation and modeling. We discuss this
difference through the relation with field-aligned current and electron
spectrum.
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