On the relation between plasma escape and the Martian crustal magnetic field

Data from ASPERA-3 on Mars Express is used to study the geographic distribution of ionospheric O(+) outflow and escape from Mars. Of particular interest is how the ion outflow relates to the crustal magnetic field regions facing the dayside, flank, and nightside of Mars. The most intense O(+) fluxes are generated on the dayside at altitudes below approximate to 1000 km, peaking over the southern hemisphere in the longitude sector 120 degrees-250 degrees. This sector coincides with the strongest crustal magnetic field regions at Mars. On the other hand, the correspondence between dayside and nightside O(+) fluxes is weak, i.e. the tailward transport of dayside O(+) ions is apparently inhibited. This suggests that most ionospheric O(+) ions on crustal magnetic field lines remain on the dayside. The dayside "mini-magnetospheres" developed acts as cellular structures recycling ionospheric plasma and reducing the tailward transport and escape of ionospheric plasma. Further support for this is that the O(+) flow over the southern hemisphere deviates strongly from the tailward northern hemisphere flow, leading to eddy structures over the southern polar cap. Citation: Lundin, R., S. Barabash, M. Yamauchi, H. Nilsson, and D. Brain (2011), On the relation between plasma escape and the Martian crustal magnetic field, Geophys. Res. Lett., 38, L02102, doi: 10.1029/2010GL046019.