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P: Plasmaphysik
P 18: Astrophysikalische und extraterrestrische Plasmen
P 18.4: Talk
Wednesday, March 20, 2002, 17:25–17:40, HZO 70
Temperature anisotropy and pitch-angle diffusion of protons in the Earth’s magnetosheath — •Claudia-Veronika Meister1, Mikhail Pudovkin2, Bruno Besser3, and Svetlana Zaitseva2 — 1Space Plasma Physics, Potsdam, Germany — 2State University, St. Petersburg, Russia — 3Space Research Institute, Graz, Austria
Experimental data show that the solar wind plasma is essentially anisotropic, especially in shocked regions, such as interplanetary shocked waves and planetary magnetosheaths. The anisotropy originates from the relatively independent evolution of the plasma temperatures in the directions parallel and perpendicular to the local magnetic field in an almost collisionless plasma. In the present paper, the dependence of the proton temperature anisotropy in the Earth’s magnetosheath on rather intensive wave turbulence excited by the anisotropy itself is discussed. The waves are mainly locally excited mirror and ion-cyclotron ones, or they have an external origin. It is concluded that the main difficulties in developing numerical magnetohydrodynamic models of the Earth’s magnetosheath are associated with the absence of a proper non-linear theory of temperature anisotropy driven plasma instabilities and with the problem of the correct choice of the form of the proton pitch-angle diffusion term. Further, first estimates of the proton temperature relaxation time are presented. These estimates are found fitting the relaxation time to fields of density, temperature, magnetic field and velocity data measured by satellites.