Articles | Volume 33, issue 6
ANGEO Communicates
12 Jun 2015
ANGEO Communicates |  | 12 Jun 2015

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

N. Jain and A. S. Sharma

Abstract. This paper presents the first evidence of a new and unique feature of spontaneous reconnection at multiple sites in electron current sheet, viz. a "nested quadrupole" structure of the Hall field at electron scales, in Cluster observations. The new nested quadrupole is a consequence of electron-scale processes in reconnection. Whistler response of the upstream plasma to the interaction of electron flows from neighboring reconnection sites produces a large-scale quadrupole Hall field enclosing the quadrupole fields of the multiple sites, thus forming a nested structure. Electron-magnetohydrodynamic simulations of an electron current sheet yields a mechanism of the formation of a nested quadrupole.

Short summary
In magnetic reconnection in collisionless plasmas, a quadrupole structure of the magnetic field component in the direction of current supporting the reconnecting magnetic field is generated down to electron scales. This paper shows that the magnetic field can develop a "nested structure of quadrupoles" at the electron scales and identifies the nested structure in Cluster observations. Results are useful in interpreting the electron physics in observations, in particular by the NASA/MMS mission.