MGS MAG/ER Observations at the Magnetic Pileup Boundary of Mars: Draping Enhancement and Low Frequency Waves

BERTUCCI, C., MAZELLE, C., CRIDER, D.H., MITCHELL, D.L., SAUER, K., ACUÑA, M.H., CONNERNEY, J.E.P., LIN, R.P., NESS, N.F., WINTERHALTER, D.

ADVANCES IN SPACE RESEARCH

Elsevier

Lugar: Amsterdam; Año: 2004 vol. 33 p. 1938 - 1944

0273-1177

The magnetic pileup boundary (MPB) is a sharp, thin, and permanent plasma boundary reported, up to now, at comets and Mars, and located between the bow shock and the ionospheric boundary. The MPB separates the magnetosheath, a region with high wave activity, from the magnetic pileup region, where the interplanetary magnetic field piles up regularly in front of the planetary obstacle. We use magnetic field and electron plasma measurements from the MAG/ER experiment onboard the Mars Global Surveyor spacecraft to study two characteristic features of the MPB. The first feature is the sudden enhancement of the magnetic field line draping at the MPB. This new signature reveals that the MPB marks the entry into the veritable induced magnetosphere, where the magnetic field topology is more regular, in opposition to what is observed in the magnetosheath. Secondly, we study the properties and the occurrence of compressive, linearly polarized, low frequency waves, frequently observed on both sides of the boundary. An analysis of the correlation between the magnetic and the electron data reveals that on the upstream side the waves are mirror mode waves, while on the downstream side they are large amplitude, quasi-monochromatic fast magnetosonic waves. The presence of these features at other atmospheric, unmagnetized bodies can be used as indicators of the existence of a MPB.