Magnetic flux generation near an O-line in collisionless reconnection— A new dynamo process

Abstract

Magnetic reconnection in a current sheet with electron gyroradius scale is studied by a full particle simulation, in which the ion-electron mass ratio is set to be mi/me=10−1836. A new dynamo process has been found in which magnetic flux emerges outward from the magnetic O-line in the magnetic island formed by reconnection. The generation of new flux is associated with plasma compression in the magnetic island. The generated new flux is estimated to be ∼B0ρe, independent of the ion-electron mass ratio, where B0 is the magnetic field far away from the current sheet, and ρe is the electron gyroradius based on B0 and the electron thermal velocity. The plasma inertia and momentum transport due to the off-diagonal elements of plasma pressure tensor can lead to E⋅J<0 near the magnetic O-line, which makes the dynamo process possible. It is also found that the characteristic time scales of the reconnection process have a power-law dependence on the ion-electron mass ratio.