Mars Global MHD Predictions of Magnetic Connectivity Between the Dayside Ionosphere and the Magnetospheric Flanks

Abstract

Atmospheric photoelectrons have been observed well above the ionosphere of Mars by the ASPERA-3 ELS instrument on Mars Express. To systematically interpret these observations, field lines from two global MHD simulations were analyzed for connectivity to the dayside ionosphere (allowing photoelectron escape). It is found that there is a hollow cylinder behind the planet from 1-2 R M away from the Mars-Sun line that has a high probability of containing magnetic field lines with connectivity to the dayside ionosphere. These results are in complete agreement with the ELS statistics. It is concluded that the high-altitude photoelectrons are the result of direct magnetic connectivity to the dayside at the moment of the measurement, and no extra trapping or bouncing mechanisms are needed to explain the data.

Estimation of the escape of photoelectrons from Mars in 2004 liberated by the ionization of carbon dioxide and atomic oxygen

“…Spacecraft rotations occurred as the spacecraft neared the planet which could cause ELS sector 3 to swing out of this orientation, and moving the signal of the distinct photoelectron peaks into other ELS sectors. The influence of spacecraft rotations on the occurrence frequency of high-altitude photoelectron observations was noted by Liemohn et al (2006b), who compared computed magnetic field line connectivity with the ELS photoelectron statistics of Frahm et al (2006b). At rare times in the martian tail, a signal which appears to be a degraded photoelectron peak can be observed flowing toward the planet; however, due to the orientation of the MEx spacecraft, the ELS signal is not clear, as the parent electron population is influenced by scatter and secondaries from the spacecraft.…”

“…At the present time, the occurrence rates over the poles are unknown. However, Liemohn et al (2006b) determined the connectivity between the polar tail regions and the dayside ionosphere from numerical simulations, showing very little high-latitude connectivity far from the planet.…”

“…The photoelectron spectra exhibit similar intensities compared to those which have previously been measured (see examples in Frahm et al, 2006a,b), and there is nothing special about the photoelectron spectrum used; however, escape rate estimates derived in this paper are dependent on the averaged electron spectrum used in the computation. The purpose of this study is to use this averaged spectrum and our previous results Liemohn et al, 2006b) that photoelectrons from the martian atmosphere are being transported down the martian tail in order to estimate the atmospheric electron loss in 2004 due to ionizations of carbon dioxide and atomic oxygen by HeII 30.4 nm photons.…”

A comparison of global models for the solar wind interaction with Mars

“…Models have also been used to investigate the structure and topology of magnetic fields in the martian system (e.g. Ma et al, 2002;Liemohn et al, 2006Liemohn et al, , 2007Harnett and Winglee, 2003;Brecht, 1990Brecht, , 1997Brecht and Ferrante, 1991;Brecht et al, 1993;Kallio et al, 2006), the influence of the solar wind on the ionosphere (e.g. Ma et al, 2004;Harnett and Winglee, 2007), plasma boundaries (e.g.…”

“…Ma et al, 2002Ma et al, , 2004Harnett and Winglee, 2003;Simon et al, 2007;Boesswetter et al, 2004;Modolo et al, 2006), and charged particle transport near Mars (e.g. Liemohn et al, 2006Liemohn et al, , 2007Fang et al, 2008, in press). Dedicated versions of these models have been developed to investigate several physical processes occurring in the martian environment such as energetic neutral atom production and transport (Gunnell et al, 2006, and references therein) or X-ray emission (Gunnell et al, 2005;Koutroumpa et al, 2006).…”