Analytical model of a magnetopause with countercurrents: multicomponent plasma with arbitrary particle energy distributions
Authors: Nechaev Anton , Kocharovsky Vitaly , Kocharovsky Vladimir 
Published: March 2021

&lt;p&gt;&lt;span&gt;We propose a&lt;/span&gt;n analytical model &lt;span&gt;f&lt;/span&gt;or a distributed current sheet separating two regions of anisotropic collisionless plasma with different values of &lt;span&gt;magnetization&lt;/span&gt; and different effective temperatures of the energy distributions of electrons and ions &lt;span&gt;[1, 2]&lt;/span&gt;. &lt;span&gt;Namely, we find a solution to the Vlasov&amp;#8211;Maxwell equations in the form of &lt;/span&gt;a superposition of arbitrary isotropic &lt;span&gt;distribution functions&lt;/span&gt; of particle &lt;span&gt;energy&lt;/span&gt;, &lt;span&gt;each &lt;/span&gt;multiplied by a Heaviside step function &lt;span&gt;of&lt;/span&gt; one of the projections of the generalized momentum. This solution admits the shear of magnetic &lt;span&gt;field&lt;/span&gt; lines and the presence of several ion components with different effective temperatures and localized countercurrents &lt;span&gt;with arbitrary densities and spatial shifts&lt;/span&gt;.&lt;/p&gt;&lt;p&gt;It is shown that &lt;span&gt;a&lt;/span&gt; &lt;span&gt;certain&lt;/span&gt; &lt;span&gt;choice &lt;/span&gt;of the energy distribution of particles (Maxwellian, kappa, and others) &lt;span&gt;determine only the &lt;/span&gt;quantitative, not qualitative, properties of the constructed models. &lt;span&gt;Sheets&lt;/span&gt; containing several fractions of particles with countercurrents, shifted relative to each other in space and having different scales, allow multiple non-monotonic changes in the magnetic field value and direction. The total &lt;span&gt;thickness of the current &lt;/span&gt;&lt;span&gt;sheet&lt;/span&gt; is determined by the values &lt;span&gt;o&lt;/span&gt;f &lt;span&gt;s&lt;/span&gt;hifts between &lt;span&gt;the &lt;/span&gt;currents of &lt;span&gt;the &lt;/span&gt;&lt;span&gt;plasma&lt;/span&gt; fractions with the highest energy content and &lt;span&gt;by &lt;/span&gt;the typical gyroradii of the&lt;span&gt;ir&lt;/span&gt; particles.&lt;/p&gt;&lt;p&gt;&lt;span&gt;We carried out p&lt;/span&gt;&lt;span&gt;article-in-cell &lt;/span&gt;&lt;span&gt;simulati&lt;/span&gt;ons of &lt;span&gt;the &lt;/span&gt;analytically constructed magnetic transition layers in one-dimensional and two-dimensional geometries. The stability of the simplest models of the considered class is demonstrated, which is consistent with qualitative estimates of stability against Weibel-type perturbations.&lt;/p&gt;&lt;p&gt;The proposed models make it possible to interpret&lt;span&gt; modern &lt;/span&gt;data of satellite observations of multicomponent current sheets in the regions of &lt;span&gt;the &lt;/span&gt;magnetopause &lt;span&gt;and &lt;/span&gt;the bow shock, solar wind magnetic clouds and high coronal magnetic structures, and to analyze the&lt;span&gt;ir&lt;/span&gt; fine structure taking into account the observed suprathermal, nonequilibrium particle fractions.&lt;/p&gt;&lt;p&gt;The investigation of stability of current sheets was supported by the Russian Science Foundation under grant No. 20-12-00268.&lt;/p&gt;&lt;p&gt;&lt;span&gt;1. K&lt;/span&gt;&lt;span&gt;ocharovsky V. V., Kocharovsky Vl. V., Martyanov V. Yu., Nechaev A. A. An analytical model for the current structure of the magnetosheath boundary in a collisionless plasma // Astron. Lett. 2019. V. 45, No. 8. P. 551&amp;#8211;564. doi:10.1134/S1063773719080048 .&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;2. &lt;/span&gt;&lt;span&gt;Kocharovsky V. V., Kocharovsky Vl. V., Nechaev A. A.&lt;/span&gt; &lt;span&gt;Analytical model of a magnetopause in a multicomponent collisionless plasma with a kappa energy distribution of particles &lt;/span&gt;&lt;span&gt;// &lt;/span&gt;&lt;span&gt;Doklady Physics&lt;/span&gt;&lt;span&gt;. 2021. &lt;/span&gt;&lt;span&gt;V&lt;/span&gt;&lt;span&gt;. 496. &lt;/span&gt;&lt;span&gt;In press.&lt;/span&gt;&lt;/p&gt;