MAGNETOSHEATH STRUCTURE IN AN ANISOTROPIC PLASMA MODEL BRUNO P. BESSER Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften, Inffeldgasse 12, A-8010 Graz, Austria; E-mail: bruno.besser@oeaw.ac.at MIKHAIL I. PUDOVKIN, VALENTINAV. LEBEDEVA and SVETLANA A. ZAITSEVA Institute of Physics, St. Petersburg State University, 198904 St. Petersburg, Russia CLAUDIA-VERONIKA MEISTER Astrophysikalisches Institut Potsdam, An der Sternwarte 12, 14482 Potsdam, Germany Abstract. Variations of the magnetic field and plasma parameters across the Earth’s magnetosheath are calculated for an anisotropic plasma in the Chew-Goldberger-Low approximation. Additionally, proton pitch-angle diffusion is taken into account as the energy transfer mechanism between the direction perpendicular and parallel to the magnetic field. We discuss the main characteristics of the magnetic barrier for different temperature relaxation times and their dependence on the interplanetary magnetic field orientation. 1. Introduction In front of streamlined obstacles in the highly conductive solar wind there forms a region, where the magnetic field increases and the plasma density decreases. To explain the formation of this so-called magnetic barrier or depletion layer a series of models have been proposed (Zwan and Wolf, 1976; Pudovkin and Semenov, 1977; Pudovkin et al., 1982; Pudovkin et al., 1995; Erkaev, 1989; Ogino et al., 1992). On the other hand, it is a well known experimental fact that the solar wind plasma in the magnetosheath is essentially anisotropic (see e.g. Hau et al., 1993; Denton et al., 1994; Phan et al., 1994). But only a few models have been developed so far to take this into account (Denton et al., 1994; Denton et al., 1995; Denton and Lyon, 1996). Recently, Pudovkin et al. (1999) studied this problem in more detail and investigated the influence of the interplanetary magnetic field (IMF) orientation and intensity and the role of magnetic reconnection at the magnetopause on the magnetosheath parameters. In this paper we want to present results of an investigation of the magnetosheath structure for different strengths of particle pitch-angle scattering. Astrophysics and Space Science 274: 399–405, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands.