Pumping out the atmosphere of Mars through solar wind pressure pulses

Abstract

We study atmospheric escape from Mars during solar wind pressure pulses. During the solar minimum of 2007-08 we have observed 41 high pressure events, which are predominantly identified as corotating interaction regions (CIR) while a few are coronal mass ejections (CME), in data from the Advanced Composition Explorer (ACE) upstream of the Earth. 36 of these events are also identified using Mars Express (MEX) data at Mars. We use MEX measurements at Mars to compare the antisunward fluxes of heavy planetary ions during the passage of these pulses to the fluxes during quiet solar wind conditions. The ion fluxes are observed to increase by a factor of ∼2.5, on average. Hence, a third of the total outflow from Mars takes place during ∼15% of the time, when a solar wind pressure pulse impacts on the planet. This can have important consequences for the total time-integrated outflow of plasma from Mars. Copyright 2010 by the American Geophysical Union.