Forced current sheet structure, formation and evolution: application to magnetic reconnection in the magnetosphere

Abstract

Part of Special Issue "Spatio-temporal analysis and multipoint measurements in space"Abstract. By means of a simulation model, the earlier predicted nonlinear kinetic structure, a Forced Kinetic Current Sheet (FKCS), with extremely anisotropic ion distributions, is shown to appear as a result of a fast nonlinear process of transition from a previously existing equilibrium. This occurs under triggering action of a weak MHD disturbance that is applied at the boundary of the simulation box. In the FKCS, current is carried by initially cold ions which are brought into the CS by convection from both sides, and accelerated inside the CS. The process then appears to be spontaneously self-sustained, as a MHD disturbance of a rarefaction wave type propagates over the background plasma outside the CS. Comparable to the Alfvénic discontinuity in MHD, transformation of electromagnetic energy into the energy of plasma flows occurs at the FKCS. But unlike the MHD case, "free" energy is produced here: dissipation should occur later, through particle interaction with turbulent waves generated by unstable ion distribution being formed by the FKCS action. In this way, an effect of magnetic field "annihilation" appears, required for fast magnetic reconnection. Application of the theory to observations at the magnetopause and in the magnetotail is considered.

Drift modes of a quasi-two-dimensional current sheet

“…The results of these studies are consistent in many respects with numerical simulation results [33,34] and earlier esti mates [35]. At present, the TCS theory is presented by two groups of analytical models ( [3,36] and [37,38]) and a number of numerical models of the TCS struc ture and formation mechanisms [39][40][41][42].…”

The Acceleration of Outer-Belt Electrons by Localized Electric Fields

“…Such localized short-term plasma flows arise as a result of bursts of magnetic reconnection in the geomagnetic tail, which form extremely thin current structures in the plasma sheet, anisotropic forced kinetic current sheets (FKCS) (Domrin and Kropotkin, 2007;Zelenyi et al, 2016;Kropotkin, 2014;Kropotkin and Domrin, 2009;Domrin and Kropotkin, 2004;Domrin, 1996, 2009;Kropotkin et al, 1997;Nakamura et al, 2006;Zhou et al, 2009). In the central part of such a sheet, under the action of the reconnection electric field, plasma is transported along the sheet to the Earth at a rate close to the local Alfvén speed, i.e., a fast localized short-term plasma flow arises.…”