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Ann. Geophys., 22, 2291-2300, 2004
www.ann-geophys.net/22/2291/2004/
© European Geosciences Union 2004
Electric field scales at quasi-perpendicular shocks
S. N. Walker1, H. St. C. K. Alleyne1, M. A. Balikhin1, M. André2, and T. S. Horbury3
1Department of Automatic Control and Systems Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK
2Swedish Institute of Space Physics, Uppsala Division, Box 537, SE-751 21 Uppsala, Sweden
3Blackett Laboratory, ICSTM, Prince Consort Road, London. UK
Abstract. 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/ωpe. The relationships between the scale size and the upstream Mach number and
θBn are studied. It is found that the scale size of these
structures decreases with increasing plasma β and as
θBn→90°. The amplitude of the spikes remains
fairly constant with increasing Ma and appears to increase as
θBn→90°.
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