P13D-07
A Substantial Plume of Escaping Planetary Ions in the MSE Northern Hemisphere Observed by MAVEN
Monday, 14 December 2015: 15:10
2009 (Moscone West)
Yaxue Dong1, Xiaohua Fang1, Dave A Brain2, James P McFadden3, Jasper S Halekas4, John E P Connerney5, Shannon Curry3, Yuki Harada3, Janet G Luhmann3 and Bruce Martin Jakosky1, (1)University of Colorado at Boulder, Boulder, CO, United States, (2)University of Colorado at Boulder, Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (3)University of California Berkeley, Berkeley, CA, United States, (4)University of Iowa, Physics and Astronomy, Iowa City, IA, United States, (5)NASA Goddard Space Flight Center, Greenbelt, MD, United States
Abstract:
The Mars-solar wind interaction accelerates and transports planetary ions away from Mars through a number of processes, including pick-up by the electromagnetic fields. The Mars Atmospheric and Volatile EvolutioN (MAVEN) spacecraft has frequently detected strong escaping planetary ion fluxes in both tailward and upstream solar wind motional electric field directions since the beginning of its science phase in November 2014. Our statistical study using three-month MAVEN data from November 2014 through February 2015 illustrates a substantial plume-like escaping planetary ion population organized by the upstream electric field with strong fluxes widely distributed in the northern hemisphere of the Mars-Sun-Electric-field (MSE) coordinate system, which is generally consistent with model predictions. The plume constitutes an important planetary ion escape channel from the Martian atmosphere in addition to the tailward escape. The >25eV O+ escape rate through the plume is estimated to be ~35% of the tailward escape and ~25% of the total escape. We will compare the dynamics of the plume and tailward escaping ions based on their velocity-space distributions with respect to the electromagnetic fields. We will also discuss the variations of the plume characteristics between different ion species (O+, O2+, and CO2+) and from the effect of different solar wind and interplanetary magnetic field (IMF) conditions.
