Tracing solar wind plasma entry into the magnetosphere using ion-to-electron temperature ratio

B. Lavraud (1) , J. E. Borovsky (2) , Vincent Génot (1) , S. J. Schwartz (3) , J. Birn (4) , A. N. Fazakerley (5) , M. W. Dunlop (6) , M. G. G. T. Taylor (7) , H. Hasegawa (8) , A. P. Rouillard (9) , J. Berchem (10) , Y. Bogdanova (5) , D. Constantinescu (11) , I. Dandouras (1) , J. P. Eastwood (12) , C. P. Escoubet (7) , H. Frey (12) , C. Jacquey (1) , E. Panov (13) , Z. Y. Pu (14) , Chao Shen (15) , J. Shi (16) , D. G. Sibeck (17) , M. Volwerk (18) , J. A. Wild (19)

1 CESR - Centre d'étude spatiale des rayonnements
2 Space Science and Applications
3 Blackett Laboratory
4 LANL - Los Alamos National Laboratory
5 MSSL - Mullard Space Science Laboratory
6 RAL Space - Space Science and Technology Department [Didcot]
7 RSSD - Research and Scientific Support Department, ESTEC
8 ISAS - Institute of Space and Astronautical Science
9 School of Physics and Astronomy [Southampton]
10 IGPP - Institute of Geophysics and Planetary Physics [Los Angeles]
11 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
12 SSL - Space Sciences Laboratory [Berkeley]
13 IKI - Space Research Institute of the Russian Academy of Sciences
14 School of Earth and Space Sciences
15 School of Science
16 CSSAR - Center for Space Science and Applied Research [Beijing]
17 GSFC Laboratory for Solar and Space Physics
18 IWF - Space Research Institute of Austrian Academy of Sciences
19 Department of Communication Systems, InfoLab 21

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.

Mots clés: Magnetospheric Physics: Magnetopause and boundary layers; Magnetospheric Physics: Magnetosheath; Space Plasma Physics: Plasma energization; Space Plasma Physics: Transport processes; Interplanetary Physics: Coronal mass ejections (7513)

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Planétologie et astrophysique de la terre [astro-ph.EP]

B. Lavraud, J. E. Borovsky, Vincent Génot, S. J. Schwartz, J. Birn, et al.. Tracing solar wind plasma entry into the magnetosphere using ion-to-electron temperature ratio. 2009. ⟨hal-00422150⟩