Lavraud, B. and Borovsky, J.E. and Genot, V. and Schwartz, S.J. and Birn, J. and Fazakerley, A.N. and Dunlop, M.W. and Taylor, M.G.G.T. and Hasegawa, H. and Rouillard, A.P. and Berchem, J. and Bogdanova, Y.V. and Constantinescu, D. and Dandouras, I. and Eastwood, J.P. and Escoubet, C.P. and Frey, H. and Jacquey, C. and Panov, E. and Pu, Z.Y. and Shen, C. and Shi, J. and Sibeck, D.G. and Volwerk, M. and Wild, James A. (2009) Tracing solar wind plasma entry into the magnetosphere using ion-to-electron temperature ratio. Geophysical Research Letters, 36. L18109. ISSN 0094-8276
Abstract
When the solar wind Mach number is low, typically such as in magnetic clouds, the physics of the bow shock leads to a downstream ion-to-electron temperature ratio that can be notably lower than usual. We utilize this property to trace solar wind plasma entry into the magnetosphere by use of Cluster measurements in the vicinity of the dusk magnetopause during the passage of a magnetic cloud at Earth on November 25, 2001. The ion-to-electron temperature ratio was indeed low in the magnetosheath (Ti/Te ∼ 3). In total, three magnetopause boundary layer intervals are encountered on that day. They all show that the low ion-to-electron temperature ratio can be preserved as the plasma enters the magnetosphere, and both with and without the observation of Kelvin-Helmholtz activity. This suggests that the ion-to-electron temperature ratio in the magnetopause boundary layer, which is usually high, is not prescribed by the heating characteristics of the plasma entry mechanism that formed these boundary layers. In the future, this property may be used to (1) further trace plasma entry into inner regions and (2) determine the preferred entry mechanisms if other theoretical, observational and simulation works can give indications on which mechanisms may alter this ratio.