Observations of Kinetic-Scale Magnetic Hole With Significant Energy Conversion in a Magnetotail Reconnection Diffusion Region

Abstract

Kinetic-scale magnetic holes (KSMHs) are ubiquitous quasi-steady magnetic structures and vital energy conversion channels in various space plasmas, for example, terrestrial foreshock and magnetopause reconnection region. However, the energy conversion mechanism within KSMHs remains unclear. We identified a KSMH within the magnetotail reconnection diffusion region by Magnetospheric Multiscale mission. Fortuitously, two spacecraft crossed the opposite half of this KSMH while the other two spacecraft didn't detect it, which offers a unique opportunity to reveal the properties inside KSMH. We find that the angle between the KSMH's axial and the out-of-plane direction of reconnection is about 60°. The non-ideal energy conversion provided by this KSMH is comparable in intensity to that within the electron diffusion region. The non-ideal electric field within the KSMH is balanced by the pressure gradient term in the electron momentum equation. These findings advance our understanding of the energy conversion mechanisms inside KSMH in space plasma.