Rotational/ Compressional nature of the Magnetopause: application of the BV technique on a magnetopause case study

Abstract

The magnetopause boundary implies two kinds of variations: a density/ temperature gradient and a magnetic field rotation. These two kinds are always observed in a close vicinity of each other, if not inseparably mixed. We present a case study from the Cluster data where the two are clearly separated and investigate the natures of both layers. We evidence that the first one is a slow shock while the second is a rotational discontinuity. The interaction between these two kinds of discontinuities is then studied with the help of 1,5-D magnetohydrodynamics simulations. The comparison with the data is quite positive and leads to think that most of the generic properties of the magnetopause may be interpreted in this sense.