Kinetic model of force-free current sheets with non-uniform temperature

Abstract

go.warwick.ac.uk/lib-publicationsOriginal citation: Kolotkov, D. Y., Vasko, I. Y. and Nakariakov, V. M.. (2015) Kinetic model of force-free current sheets with non-uniform temperature. Physics of Plasmas, 22 (11). 112902. Permanent WRAP URL:http://wrap.warwick.ac.uk/78634 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. The kinetic model of a one-dimensional force-free current sheet (CS) developed recently by M. Harrison and T. Neukirch (Phys. Rev. Lett., vol. 6, 2009) predicts uniform distributions of the plasma temperature and density across the CS. However, in realistic physical systems inhomogeneities of these plasma parameters may arise quite naturally due to the boundary conditions or local plasma heating. Moreover, as the CS spatial scale becomes larger than the characteristic kinetic scales (the regime often referred to as the MHD limit) it should be possible to set arbitrary density and temperature profiles. Thus, an advanced model has to allow for inhomogeneities of the macroscopic plasma parameters across the CS, to be consistent with the MHD limit. In this paper we generalise the kinetic model of a force-free current sheet, taking into account the inhomogeneity of the density and temperature across the CS. In the developed model the density may either be enhanced or depleted in the CS central region. The temperature profile is prescribed by the density profile, keeping the plasma pressure uniform across the CS. All macroscopic parameters, as well as the distribution functions for the protons and electrons, are determined analytically. Applications of the developed model to current sheets observed in space plasmas are discussed.

From one-dimensional fields to Vlasov equilibria: theory and application of Hermite polynomials

“…In fact it seems to be a feature generally observed that for pressure tensors (that correspond to force-free fields) constructed in this manner (Harrison & Neukirch 2009a;Wilson & Neukirch 2011;Abraham-Shrauner 2013;Kolotkov et al 2015) the plasma-β is necessarily bounded below by unity. In a recent paper, Allanson et al (2015) used the pressure transformation techniques described above, resulting in a pressure tensor of 'multiplicative form'…”

“…In particular, forcefree current sheets are relevant for the solar corona (Priest & Forbes 2000), Jupiter's magnetotail (Artemyev, Vasko & Kasahara 2014), the Earth's magnetotail Petrukovich et al 2015) and the Earth's magnetopause (Panov et al 2011). Further relevant theoretical works on distribution functions (DFs) for (nonlinear) forcefree current sheets are, for example, Harrison & Neukirch (2009a,b), Neukirch, Wilson & Harrison (2009), Wilson & Neukirch (2011), Abraham-Shrauner (2013), Allanson et al (2015) and Kolotkov, Vasko & Nakariakov (2015).…”

“…The combination of quasineutrality (N i (A x , A y , φ) = N e (A x , A y , φ)) and a DF of the form in (1.6) results in a scalar potential that is implicitly defined as a function of the vector potential, e.g. (Schindler 2007;Harrison & Neukirch 2009b;Tasso & Throumoulopoulos 2014;Kolotkov et al 2015):…”

Force-free collisionless current sheet models with non-uniform temperature and density profiles

“…The first solution for a nonlinear force-free field was found by Harrison and Neukirch 38 (see also Ref. 39) for the force-free Harris sheet, and these solutions were later extended by Kolotkov et al 2 to allow for non-uniform density and temperature profiles (with respect to the spatial coordinate). A number of other equilibrium DFs have also been found for this field.…”

“…The DFs discussed give rise to spatially uniform temperature and density profiles, in a similar way to some of the models mentioned above. In this paper, we will extend this class of DFs to include those consistent with non-uniform temperature and density profiles, using a similar approach used by Kolotkov et al 2 for the force-free Harris sheet. As for AbrahamShrauner's DFs, the new DFs we will discuss include both the linear force-free limit and the force-free Harris sheet limit.…”