ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-22-2291-2004 Electric field scales at quasi-perpendicular shocks Walker S. N. 1 Alleyne H. St. C. K. 1 Balikhin M. A. 1 AndrĂ© M. 2 Horbury T. S. 3 Department of Automatic Control and Systems Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK Swedish Institute of Space Physics, Uppsala Division, Box 537, SE-751 21 Uppsala, Sweden Blackett Laboratory, ICSTM, Prince Consort Road, London. UK 14 07 2004 22 7 2291 2300 Copyright: © 2004 S. N. Walker et al. 2004 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/22/2291/2004/angeo-22-2291-2004.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/22/2291/2004/angeo-22-2291-2004.pdf

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<sup>-1</sup> 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 <i>c</i>/&omega;<sub><i>pe</i></sub>. The relationships between the scale size and the upstream Mach number and &theta;<sub><i>Bn</i></sub> are studied. It is found that the scale size of these structures decreases with increasing plasma &beta; and as &theta;<sub><i>Bn</i></sub>&rarr;90&deg;. The amplitude of the spikes remains fairly constant with increasing <i>M<sub>a</sub></i> and appears to increase as &theta;<sub><i>Bn</i></sub>&rarr;90&deg;.