Electron-scale nested quadrupole Hall field in Cluster observations of magnetic reconnection

摘要

This paper presents the first evidence ofa new andunique feature of spontaneous reconnection at multiple sites in electron currentsheet, viz. a "nested quadrupole" structure of the Hall field at electron scales, in Cluster observations.The new nested quadrupoleis a consequence ofelectron-scale processes in reconnection.Whistler response of the upstream plasma to the interaction of electron flowsfrom neighboring reconnection sites produces a large-scale quadrupole Hallfield enclosing the quadrupole fields of the multiple sites, thus forming anestedstructure.Electron-magnetohydrodynamic simulations of an electroncurrent sheet yields a mechanism of the formation of a nested quadrupole.