Spontaneous Reconnection

  1. Edward W. Hones Jr.
  1. K. Schindler

Published Online: 19 MAR 2013

DOI: 10.1029/GM030p0009

Magnetic Reconnection in Space and Laboratory Plasmas

Magnetic Reconnection in Space and Laboratory Plasmas

How to Cite

Schindler, K. (1984) Spontaneous Reconnection, in Magnetic Reconnection in Space and Laboratory Plasmas (ed E. W. Hones), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM030p0009

Author Information

  1. Ruhr-Universit-T Bochum, D-463 Bochum, Federal Republic of Germany

Publication History

  1. Published Online: 19 MAR 2013
  2. Published Print: 1 JAN 1984

ISBN Information

Print ISBN: 9780875900582

Online ISBN: 9781118664223

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Keywords:

  • Dissipative fluctuations;
  • Earth's magnetotail;
  • Laminar Vlasov theory;
  • Plane plasma sheets;
  • Spontaneous reconnection

Summary

Spontaneous reconnection occurs when an originally stable system, which is gradually changed by external forces, passes over an onset point of an instability involving magnetic reconnection. The prototype of the instability is the tearing mode of a plane plasma sheet. Since plane plasma sheets are always unstable, more refined theories are being developed to explain the transition from stability to instability. In the case of the earth's magnetotail, during times when microturbulence is negligible, the main stabilizing factor is a finite amount of magnetic flux passing perpendicularly through the plasma sheet. If the motion of the electrons is adiabatic, the WKB-regime (small wavelengths along the direction of the main magnetic field) is stable. A recent numerical study has established an instability for wavelengths comparable with the equilibrium scale length along the main magnetic field, A sudden appearance of fluctuations or ionospheric feed-back can lead to rapid growth. In the fluid approach the attention presently concentrates on the efficiency of the lower-hybrid-drift instability for generating the required resistivity. Several other factors that control spontaneous reconnection are discussed, among them shear in the magnetic field and in the plasma flow. Expressions for free energy available for reconnection-type instabilities are discussed, corresponding to situations with and without fluctuations. Large scale MHD-computations have largely confirmed and extended the analytical work, particularly for magnetotail configurations; there is also remarkable agreement with an empirical model. It appears that spontaneous reconnection plays a decisive role in controlling magnetic topology and in releasing previously stored free energy.