The cross-shock potential at the Earth\'s quasi-parallel bow shock: Cluster observations

R Behlke

M. Andre, S.D. Bale, H. Kucharek, E. Lucek, A. Vaivads

We present Cluster observations at the Earth\'s quasi-parallel bow shock and in particular of Short Large-Amplitude Magnetic Structures (SLAMS). These structures are commonly observed upstream or at the quasi-parallel bow shock and are thought to play an important role for the shock structure. Observations and simulations led to a model of a cyclically reforming shock which is built up of a patchwork of SLAMS. In this picture, the quasi-parallel shock is described as an extended transition region characterized by the growth, deceleration and merging of SLAMS rather than a single shock surface.

In order to evaluate the importance of SLAMS, we compare the electric cross-SLAMS potential with ion particle data. We find that the SLAMS steepen as they approach the nominal shock surface, exhibiting a increased electric potential. This is strongly correlated with the slowing down and heating of the incoming solar wind flow. Thus, SLAMS might stand for a main contribution to the all-over dissipation at quasi-parallel shocks.