Externally Driven Magnetic Reconnection
- Edward W. Hones Jr.
Published Online: 19 MAR 2013
Copyright 1984 by the American Geophysical Union.
Magnetic Reconnection in Space and Laboratory Plasmas
How to Cite
Walker, R. J. and Sato, T. (1984) Externally Driven Magnetic Reconnection, in Magnetic Reconnection in Space and Laboratory Plasmas (ed E. W. Hones), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM030p0272
- Published Online: 19 MAR 2013
- Published Print: 1 JAN 1984
Print ISBN: 9780875900582
Online ISBN: 9781118664223
- Magnetic field lines;
- Magnetic reconnection;
- Magnetohydrodynamic (MHD);
- Plasma flow and slow shock formation;
- Simulation model
We have simulated externally driven magnetic reconnection by solving the magnetohydrodynamic equations in an initially plane current sheet. Both two dimensional (2D) and 3D versions of the model have been developed. In this model, we postulate that reconnection in the tail is triggered by a local compression of the plasma sheet which results from an invasion of the solar wind into the magnetotail. Thus we start the simulation by introducing flow from the lobes normal to the plasma sheet. When resistivity is generated in a local region of the neutral sheet reconnection develops and magnetic energy is converted into plasma bulk flow. As the reconnection proceeds, the cross tail current is concentrated in two thin slow shock layers. On the downstream side of the slow shocks strong plasma flows away from the reconnection region are generated. The flows near the equator are normal to B while those in the slow shocks are along B. Near the equator the flows exceed the local magnetosonic velocity. In addition, plasma from regions adjacent to the reconnection region is drawn into the reconnection region thereby creating appreciable flows (∼ .2 VA) in the Y (cross tail) direction. Our simulation results, also, demonstrate that the night side substorrn current system is a natural consequence of driven magnetic reconnection. The dawn to dusk cross tail current is interrupted locally and field aligned currents are generated. The field aligned current flows towards the ionosphere on the morning side and away from the ionosphere in the evening. The field aligned currents flow in a narrow band at the outer edge of the plasma sheet. The extent of this field aligned current system is limited in the Y direction with the largest currents near the edges of the reconnection region. In the equatorial plane, current vortices form connecting the reconnection region and the region of reconnected field lines. In the region of reconnected field lines the current is now from dusk to dawn rather than dawn to dusk. The J×B force in this region opposes the flow from the reconnection region. The area of dusk to dawn current also is the region where the flow becomes super magnetosonic and is characterized by a rapid decrease in pressure. The sharp decrease in pressure is a fast shock. The super magnetosonic flow is maintained by this sharp pressure gradient.