A two-spacecraft study of the Martian magnetic pileup boundary: Mars Express and Mars Global Surveyor observations

We present initial results from a study of the Martian magnetic pileup boundary (MPB) using simultaneous measurements from Mars Global Surveyor (MGS) and Mars Express (MEX). MGS and MEX had almost three years of overlapping data coverage at Mars, from 2004 until late 2006 with very complementary instrumentation. MGS measured vector magnetic field and suprathermal electrons from a ~400 km circular orbit fixed in local time whereas the MEX ASPERA-3 instrument measures suprathermal electrons and ions from a precessing elliptical orbit. We use these highly complementary datasets to study asymmetries and variability in the shape of the MPB. The suprathermal electron measurements can be used to identify times when each spacecraft is in the magnetosheath " above the MPB. Simultaneous measurements will help to constrain the shape. Correlation of the boundary shape with upstream solar wind and IMF conditions measured directly by MEX and indirectly by MGS allow us to quantify the variability in the shape. We will present both case studies and a statistical analysis using these simultaneous observations.