Parallel Electric Fields Associated with Double Layers in Kappa Distributed Space Plasmas

Parallel electric field structures associated with double layers (DLs) provide the best explanation for the physical mechanism underlying charged particle energization acceleration at sites of magnetic reconnection. In-situ measurements of reconnection sites by various satellites such as MMS, THEMIS, and FAST confirmed the connection of charged particle energization with the large parallel electric fields in the auroral regions, Earth's plasma sheet, and the separatrix region of the magnetosphere. We employed the fully nonlinear Sagdeev potential technique and multi-fluid theory for electron-ion plasma to find double-layer solutions and the accompanying electric field at the reported sites. Considering electrons to be kappa distributed, we have taken into account the ion inertial effect. Specifically, at non-Maxwellian effective temperature scales, parallel electric fields related to the Alfvénic double layer have been studied and compared with the observations. We have shown that the nonthermal parameter kappa and Alfvénic Mach number 𝑀Aconsiderably alter the properties of DLs and the associated electric field of kinetic Alfvén waves.