HR: 1340h
AN: SA53B-1169    [Abstracts]
TI: Modeling of ion trajectories in Mercury's magnetosphere
AU: * Sarantos, M
EM: smenelaos@hotmail.com
AF: University of Maryland, Department of Astronomy, College Park, MD 20740 United States
AU: Reiff, P H
EM: reiff@rice.edu
AF: Rice University, Dept of Physics and Astronomy Rice Space Institute MS 108, Houston, TX 77005 United States
AU: Killen, R
EM: rkillen@astro.umd.edu
AF: University of Maryland, Department of Astronomy, College Park, MD 20740 United States
AB: This paper presents new tracings of ions in Mercury's magnetosphere that model the variability of the solar wind, sodium and potassium ion fluxes on the surface. The magnetic field is given by a modified version of the analytic Toffoletto-Hill (TH93) open magnetosphere model, which also gives the electric potential along open field lines. Its applicability is extended into the closed field line region by the Ding (1995) potential solver, which computes the realistic electric potential that is self-consistent with the magnetic field. Four cases of the solar wind and the interplanetary magnetic field (IMF) are tested, two at aphelion and two at perihelion. Photoions are launched from the scale height for each species, while solar wind ions are backtraced from the surface to the magnetopause. Photoion results reveal that impacts dominate. The prediction that recycling reduces by a factor of 1.5 at perihelion could help explain why the sodium atmosphere is denser at aphelion. In addition, tracings of Hermean ions show that differential escape losses do not exist for potassium photoions such that may explain the variable Na/K ratio in the Hermean atmosphere. Solar wind ion tracings (H+; O+7) confirm that precipitation to Mercury's surface may happen along closed field lines not only at perihelion, but even at aphelion for realistic cases of southward IMF. The computed total sputtering flux increased by a factor of 1.7 from aphelion to perihelion. We conclude that ion sputtering caused by the solar wind can explain the high-latitude variability seen in imaging data of Mercury's sodium atmosphere. Funding for this research was provided by NASA grants NAG5-11047 and NAG5-12566
DE: 0343 Planetary atmospheres (5210, 5405, 5704)
DE: 2459 Planetary ionospheres (5435, 5729, 6026)
DE: 2756 Planetary magnetospheres (5443, 5737, 6033)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005