Magnetosheath model in the Chew–Goldberger–Low approximation

Abstract

Parameters of the solar wind plasma and magnetic field in the magnetosheath are calculated for an anisotropic plasma model in the Chew–Goldberger–Low approximation. It is shown that in the case when the energy transfer between the perpendicular and parallel (with respect to the magnetic field) degrees of freedom is absent, the resulting temperature anisotropy may significantly affect the plasma density and magnetic field intensity profiles across the magnetosheath. However, in this case, the value of the temperature anisotropy (the ratio of the perpendicular to the parallel component of the temperature with respect to the magnetic field, T⊥/T‖) becomes unrealistic high. To bring agreement between the model values of the temperature anisotropy and experimental data, the existence of an intensive proton pitch-angle diffusion is assumed. In the case when the temperature anisotropy relaxation time is much smaller than the time taken by the solar wind plasma to move from the bow shock to the magnetopause, one has T⊥/T‖≈1, and the profiles of the magnetic field and plasma density along the subsolar stream line insignificantly differ from the profiles obtained for the isotropic magnetohydrodynamic (MHD) model. In an intermediate case when the relaxation time is of the order of the plasma transport time, the value of T⊥/T‖ may amount to the values observed in the magnetosheath.

Effective Polytropic Indices of Anisotropic Planetary Magnetosheath Plasmas with Magnetoacoustic Waves

“…The obtained effective polytropic indices below unity are in agreement with findings of [4]. In [4], a wave structure observed by the satellite IMP-8 in the solar wind on December 17, 1990, 04-08 UT seemed to be associated with the propagation of a slow magnetoacoustic wave.…”

“…Pudovkin et al [1,3,4] concentrated their attention on the effective value of the polytropic index γ eff which characterizes the relationship between the total thermal energy of the particles ε and the plasma mass density ρ. In their analysis, they wrote the energy equation for an anisotropic plasma in a form analogous to that in gasdynamics…”

“…Since about 35 years, numerous experimental and theoretical investigations of the polytropic index of the transition layer between the Earth's magnetic field and the solar wind, the so-called magnetosheath, were performed (see [1][2][3][4][5][6][7][8] and cited references). Recently, with the strong development of the comparative planetology, including above all also the consideration of the magnetospheres of Jupiter and Saturn, this topic got even more in the center of interest [9,10].…”

Magnetic Field Amplification and Evolution in Turbulent Collisionless Magnetohydrodynamics: An Application to the Intracluster Medium

“…Following previous works (Denton et al 1994; see also Pudovkin et al 1999;Samsonov & Pudovkin 2000;Samsonov et al 2001;Meng et al 2012a), whenever the plasma satisfies the firehose (Equation (7)) or kinetic mirror instability criteria (Equation (9)), we impose the following pressure anisotropy relaxation condition:…”

“…The simplest collisionless MHD-type approximation is the CGL-MHD model (Chew et al 1956). A modified CGL-MHD model taking into account the anisotropy constraints due to kinetic instabilities has been used for modeling the solar wind and magnetosphere in numerical simulations (Denton et al 1994;Pudovkin et al 1999;Samsonov & Pudovkin 2000;Samsonov et al 2001Samsonov et al , 2007Meng et al 2012aMeng et al , 2012b; see also Chandran et al 2011 where a higher order fluid model is used).…”