Magnetic Reconnection at the Sun
- 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
Priest, E. R. (2013) Magnetic Reconnection at the Sun, in Magnetic Reconnection in Space and Laboratory Plasmas (ed E. W. Hones), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM030p0063
- Published Online: 19 MAR 2013
- Published Print: 1 JAN 1984
Print ISBN: 9780875900582
Online ISBN: 9781118664223
- Coalescence instability;
- Magnetic reconnection;
- Solar corona;
- Solar prominences
Recent advances in reconnection theory include the realisations that reconnection may be initiated in many different ways and the tearing mode instability may develop nonlinearly along several different pathways. This resolves the dichotomy between the “forced” and “spontaneous” reconnection schools of thought, since both types of reconnection can occur, depending on the application. Also, a new regime has been discovered of impulsive bursty reconnection when the Petschek-Sonnerup regime goes unstable to tearing and rapid coalescence as pairs of X- and O-points are repeatedly created and annihilated.
In the Sun reconnection may be responsible for a wide range of phenomena. Prominences are huge sheets of plasma supported in a magnetic configuration that is thought to evolve slowly through a series of equilibria containing neutral points. The solar corona may be heated by small-scale tearing in Alfvén waves that have been phase-mixed by magnetic field inhomogeneities. Alternatively, the heating may be caused by a continuous generation of tearing turbulence as the coronal magnetic field evolves through a series of equilibria subject to a constraint on the evolution of magnetic helicity.
In solar flares reconnection may play several roles including the initial triggering of an eruptive magnetic instability by new flux emergence. Also the main phase of energy release occurs as open magnetic field lines (that are line-tied to the solar surface) close down. This process has been modelled numerically and reveals a linear tearing phase followed by a quasi-steady phase of nonlinear Petschek reconnection with slow shocks and below the reconnection site a fast shock. Later, it evolves into the impulsive bursty reconnection regime.