第八届青年地学论坛

Ion-scale and electron-scale magnetic holes widely exist in many space plasma regions, and have been extensively studied. However, characteristics of the charged particles and current densities inside the linear magnetic holes (LMHs) with a size between typical ion and electron scales are unclear. Here, we report a LMH with a cross-section size of ~2.4 ion gyroradii in the terrestrial current sheet using the high-resolution data of the Magnetospheric Multiscale mission. We find that the electron velocity and temperature have significant variations at the sharp boundaries of this LMH, while the ion parameters have no significant change. The decrease of the magnetic field pressure is mainly balanced by the electron thermal pressure. A strong electron flow accompanied by an enhancement of the electric field is formed by electron drift motions on the outermost boundary with a thickness of 0.12 – 0.24 ion gyroradius. This electric field might originate from variations of the ion and electron gyrations when crossing the sharp boundary. The electron flow forms a thin current sheet on the outermost side of the LMH instead of being distributed over the entire cross section. Most of the trapped electrons are wrapped by this thin current sheet. These results could improve our understanding of the properties of LMHs with a size between typical ion and electron scales.
 

Linear magnetic hole; Terrestrial current sheet