MGS MAG/ER Observations of Compressive low Frequency Waves at the Martian Magnetic Pileup Boundary

BERTUCCI, C. L.; MAZELLE, C.; CRIDER, D. H.; MITCHELL, D. L.; SAUER, K.; ACUNA, M. H.; CONNERNEY, J. E.; REME, H.; LIN, R. P.; CLOUTIER, P. A.; NESS, N. F.; WINTERHALTER, D.

Congreso; AGU Fall Meeting 2001; 2001

We use magnetic field and electron plasma measurements from the MAG/ER experiment onboard the Mars Global Surveyor spacecraft to study the properties of compressive, low frequency waves, which are frequently observed on both sides of the magnetic pileup boundary (MPB). This thin, sharp and permanent plasma boundary marks the end of the Martian magnetosheath which displays a high level of wave activity, and the entry in a region where the magnetic field is less disturbed, more intense, and draped around the ionospheric obstacle. On both sides of the MPB, the observed waves are linearly polarized with respect to a very steady background magnetic field. Cross-correlation analyses of the magnetic field and electron data reveal that on the upstream side, these are mirror mode waves, while downstream, large amplitude, quasi-monochromatic fast mode waves are observed. Interestingly, this same wave feature was also reported around the MPB of active comets, but never at Venus. We present the results of a statistical study on the occurrence of these waves and on their characteristics from a large set of orbits. This is completed by detailed analyses of the properties of these LF waves for some particular events. The role of these compressive LF waves at the MPB of both comets and Mars is also discussed.