Observations of a Unique Cusp Signature at Low and Mid Altitudes |
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| Authors: | W R Keith J D Winningham M L Goldstein M Wilber A N Fazakerley H Rème T A Fritz A Balogh N Cornilleau-Wehrlin M Maksimovic |
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| Institution: | (1) Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510, USA;(2) NASA Goddard Space Flight Center, Code 612.2, Greenbelt, MD 20771, USA;(3) University of California, Space Science Laboratory 7450, 94720 Berkeley, CA, USA;(4) Mullard Space Science Laboratory, Holmbury St Mary, RH5 6NT Dorking, Surrey, UK;(5) CESR, BP 4346, 9 Ave Colonel Roche, Cedex, Toulouse, 31029, France;(6) Center for Space Physics, Boston University, 725 Commonwealth Ave, Boston, MA 02215, USA;(7) The Blackett Laboratory, Imperial College Space and Atmospheric Physics group, London, UK;(8) CETP, 10-12 Ave de Europe, Velizy, 78140, France;(9) Paris Observatory, LESIA and CNRS, 61 Ave de l’Observatoire, France |
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| Abstract: | Observations of a unique cusp feature at low and mid altitudes are reported. This feature has a consistent double-peaked or “V”-shaped structure at the equatorward edge of high-latitude particle precipitation flux, and is predominantly present for high IMF By conditions. The observations are consistent with the Crooker (‘A split separator line merging model of the dayside magnetopause’, J. Geophys. Res. 90 (1985) 12104, ‘Mapping the merging potential from the magnetopause to the ionosphere through the dayside cusp’, J. Geophys. Res. (1988) 93 7338.) antiparallel merging model, which predicts a narrow wedge-shaped cusp whose geometry depends greatly on the dawn/dusk component of the IMF. Various observations are presented at low altitudes (DE-2, Astrid-2, Munin, UARS, DMSP) and at mid altitudes (DE-1, Cluster) that suggest a highly coherent cusp feature that is consistent with the narrow, wedge-shaped cusp of Crooker (1988), and contains persistent wave signatures that are compatible with previously reported high-altitude measurements. A statistical survey of Astrid-2 and DMSP satellite data is also presented, which shows this feature to be persistent and dependent on the IMF angle at the magnetopause, as expected. Thus, the cusp signatures observed at a wide range of altitudes present a coherent picture that may be interpreted in terms of a footprint of the magnetopause current layer. |
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| Keywords: | Cusp True cusp Magnetosphere |
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