Charged particles energization during magnetic reconnection in the Earth’s magnetosphere by double layers: an analytical approach

Abstract

ABSTRACT Charged particles energization at the magnetic reconnection sites in the Earth’s magnetosphere is a subject of active debate in space plasma, specifically in magnetopause and magnetotail regions. In the proximity of the reconnection region, Magnetospheric Multiscale (MMS) and other satellite missions have confirmed the existence of electron acceleration ranging from 100 keV to MeV. There is also evidence of cold ions acceleration in the separatrix region of the Earth’s magnetopause. An important candidate responsible for charged particles acceleration is believed to be the double layer (DL) structures, and which were first observed by the Cluster satellite in the separatrix region of the Earth’s magnetosphere. Moreover, the MMS mission also observed parallel electric field fluctuations up to 100 mV/m carried by DL at the magnetic reconnection site in the Earth’s magnetosphere. Motivated by the reported literature, we investigate the DL and its associated electric field at the magnetopause magnetic reconnection site by using a simple analytical model in which the DLs associated with kinetic Alfvén waves are studied in a low- $\beta$ electron-ion plasma with Tsallis distributed electrons and fluid ions using the Sagdeev potential technique. The non-extensive parameter (superthermality) of the Tsallis distribution has a pronounced effect on the DL’s strength (as defined by the potential drop) and its associated parallel electric field. Our results are consistent with the earlier studies on DLs in Earth’s magnetosphere. Additionally, we discuss the implications of our findings on charged particle energization in the separatrix region of the Earth’s magnetopause during magnetic reconnection.