P21A-2072
MAVEN MAG Observations of Magnetic Field Enhancements and Decreases in the Induced Magnetosphere of Mars
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Yasir Ibn Jilani Soobiah1, Jared R Espley1, John E P Connerney1, Gina A DiBraccio2, Jacob Gruesbeck3, Jasper S Halekas4, David L Mitchell5, James P McFadden5, Dave A Brain6 and Bruce Martin Jakosky7, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, United States, (3)University of Maryland College Park, College Park, MD, United States, (4)University of Iowa, Iowa City, IA, United States, (5)University of California Berkeley, Berkeley, CA, United States, (6)University of Colorado at Boulder, Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (7)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States
Abstract:
Recent results have shown the occurrence of a large-scale flux rope (enhancement in magnetic field strength and rotation in magnetic field vectors) on the dayside of Mars as associated with a dayside current sheet region forming at the proximity of strong crustal magnetic fields. This dayside current sheet region including the example of the large-scale flux rope occurred when the draped solar wind magnetic field showed a +By component in the MSO frame. All events involved similar anisotropic pitch angle distribution of electrons with low-energy field aligned electrons and higher-energy trapped electrons, indicating either the mixing of trapped magnetosheath electrons with low energy field aligned ionospheric electrons and/or the pitch angle diffusion of ionospheric electrons. During a time of weak draped field, the current sheet region became highly extended and was observed alongside a decrease in magnetic field strength and highly anisotropic plasma indicative of a mirror mode structure or magnetic hole. The occurrence of magnetic decreases or magnetic holes are an established feature of the solar wind and are often found in the terrestrial magnetosheath, and have also been observed near Jupiter, Venus and comets. More recently, mirror mode structures have been reported within the Earth’s magnetosphere. The occurrence of the mirror mode instability could result in the excitation of ULF waves and has also been related to Alfvén waves that could cause heating of the local plasma. Hence, both the large-scale flux ropes and mirror mode structures of current sheet regions on the dayside of Mars may have an important role in ionospheric heating and atmospheric escape at Mars. Therefore, using an automated routine we will attempt to search for the occurrence of magnetic field enhancements and magnetic field decreases in measurements of magnetic field by the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite Magnetometer (MAG) instrument whilst comparing to the other Particle and Fields Package (PFP) instruments to further explore the properties of the large-scale flux ropes and magnetic mirror instability at Mars and assess their role in the escape of the Martian atmosphere.
