P21A-2080
Pressure balance across large magnetic flux ropes on the dayside of Mars
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Catherine Dieval1, James A Wild2, John E P Connerney3, Robert E Ergun4, Bruce Martin Jakosky5, David L Mitchell6, James P McFadden6 and Jasper S Halekas7, (1)University of Lancaster, Department of Physics, Lancaster, United Kingdom, (2)University of Lancaster, Lancaster, United Kingdom, (3)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (4)University of Colorado, Boulder, CO, United States, (5)LASP, University of Colorado at Boulder, Boulder, CO, United States, (6)University of California Berkeley, Berkeley, CA, United States, (7)University of Iowa, Physics and Astronomy, Iowa City, IA, United States
Abstract:
Large cylindrical structures of highly twisted magnetic field (magnetic flux ropes) have been observed on the dayside of Mars, downstream of the crustal magnetic fields, by several missions: Mars Global Surveyor, Mars Express and MAVEN. Signatures of flux ropes are spikes of magnetic field strength and magnetic field rotations. Using a minimum variance analysis of the MAVEN magnetometer data, we identify cases of large magnetic flux ropes downstream of crustal fields in the dayside Martian ionosphere. We also analyse concurrent plasma observations inside these structures performed with STATIC, SWEA, SWIA and LPW. A question of interest is the pressure balance across the flux ropes: if the increased magnetic pressure inside these structures is not associated with a thermal pressure decrease, then they are force-free. We use the MAVEN measurements to investigate the force-free or non force-free state of a number of flux ropes, and any dependence of such state on various parameters. The results are analysed in the light of previous studies made with measurements of small flux ropes in the Venusian ionosphere by Pioneer Venus Orbiter.
