Electric field scales at quasi-perpendicular shocks
This paper investigates the short scale structures that are observed in the electric field during crossings of the quasi-perpendicular bow shock using data from the Cluster satellites. These structures exhibit large amplitudes, as high as 70 m Vm -1 and so make a significant contribution to the overall change in potential at the shock front. It is shown that the scale size of these short-lived electric field structures is of the order of a few c/ω pe. The relationships between the scale size and the upstream Mach number and θ Bn are studied. It is found that the scale size of these structures decreases with increasing plasma β and as θ Bn→90°. The amplitude of the spikes remains fairly constant with increasing Ma and appears to increase as θ Bn→90°.