Thermodynamics of the magnetotail current sheet thinningстатья
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Дата последнего поиска статьи во внешних источниках: 17 июня 2021 г.
Аннотация:Substorm growth phase in the magnetotail is characterized by formation of a thin current sheet becomes unstable due to external or internal drivers. Such instability results in magnetic field line reconnection, the substorm onset. The current sheet thinning, as a key process of substorm dynamics, has been included into many global and local simulations of the magnetotail magnetic reconnection. However, recent observations indicate that the evolution of plasma characteristics and magnetic field configuration during the current sheet thinning can differ from predictions of the classical adiabatic scenario. In this paper we combine two most extensive datasets of the current sheet evolution, as observed by Cluster and THEMIS missions for 2001‐2009 and 2015 respectively. We show that for a wide range of downtail distances and dawn‐dusk direction there are quite similar quantitative characteristics of the thinning: the magnetic field line stretching (north‐south magnetic field decrease), the intensification of the current density, and the evolution of plasma temperatures and densities. We confirm that the process can not be directly associated with increase of the lobe magnetic pressure. Using advantages of multispacecraft measurements and current sheet flapping motion, we demonstrate that the thinning is usually result in the equatorial density increase and plasma temperature decrease. We discuss the revealed evolution features in the context of the thermodynamical current sheet characteristics for contemporary thinning models.