Abstract
AbstractThe NASA Magnetospheric Multiscale mission has made in situ diffusion region and kinetic‐scale resolution measurements of asymmetric magnetic reconnection for the first time, in the Earth's magnetopause. The principal theoretical tool currently used to model collisionless asymmetric reconnection is particle‐in‐cell simulations. Many particle‐in‐cell simulations of asymmetric collisionless reconnection start from an asymmetric Harris‐type magnetic field but with distribution functions that are not exact equilibrium solutions of the Vlasov equation. We present new and exact equilibrium solutions of the Vlasov‐Maxwell system that are self‐consistent with one‐dimensional asymmetric current sheets, with an asymmetric Harris‐type magnetic field profile, plus a constant nonzero guide field. The distribution functions can be represented as a combination of four shifted Maxwellian distribution functions. This equilibrium describes a magnetic field configuration with more freedom than the previously known exact solution and has different bulk flow properties.
Highlights
The formation of current sheets is ubiquitous in plasmas
We present new and exact equilibrium solutions of the Vlasov-Maxwell system that are self-consistent with one-dimensional asymmetric current sheets, with an asymmetric Harris-type magnetic field profile, plus a constant non-zero guide field
The equilibrium distribution function (DF) in equation (8) is written as a function of the constants of motion (Hs, pxs, pys), which was suitable for constructing an exact equilibrium solution to the Vlasov equation
Summary
The formation of current sheets is ubiquitous in plasmas. The plasma conditions on either side of the current sheet can be different, e.g. the magnetic field strength and orientation. The asymmetric feature has been included in modelling the reconnection rate [Cassak and Shay, 2007], the development of the lowerhybrid instability [Roytershteyn et al, 2012] and the suppression of reconnection at Earth’s magnetopause [Swisdak et al, 2003; Phan et al, 2013; Trenchi et al, 2015; Liu and Hesse, 2016]. Developing an exact Vlasov equilibrium for the current sheet is important, but it is challenging. We present a new exact Vlasov-Maxwell equilibrium solution for asymmetric current sheets. Working within the confines of an exact model does imply that we cannot accurately represent all desired features of the magnetopause current sheet system, and some of these restrictions will be discussed
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