Collisionless Plasma Expansion in the Presence of a Dipole Magnetic Field

Abstract

Key wordsThe collisionless interaction of an expanding high-energy plasma cloud with a magnetized background plasma in the presence of a dipole magnetic field is examined in the framework of a 2D3V hybrid (kinetic ions and massless fluid electrons) model. The retardation of the plasma cloud and the dynamics of the perturbed electromagnetic fields and the background plasma are studied for high Alfvén-Mach numbers using the particle-incell method. It is shown that the plasma cloud expands excluding the ambient magnetic field and the background plasma to form a diamagnetic cavity which is accompanied by the generation of a collisionless shock wave. The energy exchange between the plasma cloud and the background plasma is also studied and qualitative agreement with the analytical model suggested previously is obtained.

Self-similar analytical model of plasma expansion in a magnetic field

“…Therefore, one can expect that the spherical shape of the plasma is deformed into the ellipsoidal one which is elongated along the magnetic field lines. This effect is supported by the numerical simulations [4,5]. Thus, the isotropic self-similar model considered here is valid as long as the deformation of the plasma shape is much smaller than the typical length scale for the plasma flow.…”

“…Estimating accuracy of the free expansion model, one should take into account that the long stage of plasma deceleration corresponds to a high expansion ratio, a(t)/a 0 ≫ 1. Average plasma pressure drops significantly and plays no role in energy balance equation (5) during this stage. In accordance with the above boundary condition local pressure near the plasma edge must be equal to the magnetic pressure outside.…”

“…Substituting equations (6)-(8) into (5) and integrating over r yields first-order differential equation for a(t), which already satisfies initial conditionȧ(0) = v m ,…”

An exact solution of the moving boundary problem for the relativistic plasma expansion in a dipole magnetic field

“…For instance, an important example is the expansion of a plasma cloud with a sharp boundary across an ambient magnetic field. Such kind of processes are particularly of interest for many space and laboratory investigations (see [5][6][7][8][9] and references therein). This is a topic of intense interest across a wide variety of disciplines within plasma physics, with applications to laser generated plasmas [9], solar [10] a e-mail: hrachya@irphe.am and magnetospheric [11,12] physics, astrophysics [13], and pellet injection for tokamak refueling [14].…”

Resistive magnetohydrodynamic model for cylindrical plasma expansion in a magnetic field

“…[1][2][3][4][5] and references therein). In particular, such process is a topic of intense interest across a wide variety of disciplines, with applications to solar [6] and magnetospheric [7,8] physics, astrophysics [9], and pellet injection for tokamak refueling [10].…”