Suppression of Hall-Term Effects by Gyroviscous Cancellation in Steady Collisionless Magnetic Reconnection

The formation of an ion-dissipation region, in which motions of electrons and ions decouple and fast magnetic reconnection occurs, is demonstrated during a steady state of two-dimensional collisionless driven reconnection by means of full-particle simulations. The Hall-term effect is suppressed due to the gyroviscous cancellation at scales between the ion-skin depth and ion-meandering-orbit scale, and thus ions are tied to the magnetic field. The ion frozen-in constraint is strongly broken by nongyrotropic pressure tensor effects due to ion-meandering motion, and thus the ion-dissipation region is formed at scales below the ion-meandering-orbit scale. A similar process is observed in the formation of an electron-dissipation region. These two dissipation regions are clearly observed in an out-of-plane current density profile.

Figure 1

The perspective view of the out-of-plane current density profile on the $xy$ plane in the steady state.

Figure 2

The spatial profile of the out-of-plane current density along the vertical line passing the $X$ point in the steady state.

Figure 3

The spatial profile of each term in the out-of-plane component of the ion momentum equation and of the electron momentum equation along the vertical line passing the $X$ point in the steady state.

Figure 4

The spatial profile of the out-of-plane ion flow velocity (solid line) and the out-of-plane ion diamagnetic flow velocity (dotted line) along the vertical line passing the $X$ point in the steady state.