Magnetic Field Line Draping Enhancement Across The Martian Magnetic Pileup Boundary

BERTUCCI, C.; MAZELLE, C.; CRIDER, D.; VIGNES, D.; ACUÑA, M.; SAUER, K.; CONNERNEY, J.; RÈME, H.; MITCHELL, D.; LIN, R.; CLOUTIER, P.; NESS, N.; WINTERHALTER, D.

Congreso; EGS XXVII General Assembly; 2002

The Magnetic Pileup Boundary (MPB) is a thin, sharp and permanent plasma bound- ary located between the bow shock and the ionosphere of Mars and comets. This boundary marks the end of the Martian magnetosheath, which displays a high level of wave activity, and the entry in a inner region where the magnetic field is less dis- turbed, and piles up regularly around the planetary obstacle (magnetic pileup region or magnetic barrier). Although a sharp jump in the magnetic field intensity is not nec- essarily observed at the MPB, it is always characterized by a significant change of the spectrum of suprathermal electrons with a sharp decrease of their fluxes, and by a clear change in the magnetic field topology. We analyse Mars Global Surveyor mag- netometer data to show that the draping of field lines is suddenly enhanced as soon as the MPB is crossed, and the magnetic field topology becomes much more regu- lar downstream the boundary. These results are found to be consistent with those at comets when applying the same technique. This shows that the draping enhancement at the MPB is a common feature for comets and Mars.