Formation of Flux Ropes by Turbulent Reconnection
- C. T. Russell,
- E. R. Priest and
- L. C. Lee
Published Online: 21 MAR 2013
Copyright 1990 by the American Geophysical Union.
Physics of Magnetic Flux Ropes
How to Cite
Lysak, R. L. and Song, Y. (1990) Formation of Flux Ropes by Turbulent Reconnection, in Physics of Magnetic Flux Ropes (eds C. T. Russell, E. R. Priest and L. C. Lee), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM058p0525
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1990
Print ISBN: 9780875900261
Online ISBN: 9781118663868
- Solar photosphere;
- Magnetic flux;
Although traditional reconnection models have assumed a two-dimensional geometry and steady-state conditions, reconnection at the earth's magnetopause and in other applications is likely to be time-dependent, turbulent, and three-dimensional in nature. At the high magnetic Reynolds numbers present in most reconnection sites, the evolution of the plasma is expected to follow nearly ideal MHD conditions. Under these conditions, the invariants of three-dimensional MHD, namely the energy, magnetic helicity, and the cross helicity are expected to be conserved. When ideality is violated in a localized region, the energy is dissipated at a higher rate than the other two invariants, so that the magnetic helicity is essentially conserved during the reconnection process. In addition, during the three-dimensional evolution of an MHD fluid, magnetic helicity undergoes an inverse cascade to large scales, indicating that a region in which many small-scale reconnections take place will self-organize into a large scale flux rope.
A magnetic flux rope intrinsically contains magnetic helicity which exhibits itself topologically in the twisting of the rope. Under the above scenario, this helicity can be produced by the transformation of helicity contained in the topology of the flux tubes which existed before reconnection. Such a model can satisfactorily account for the amount of twist observed in flux transfer event (FTE) flux ropes. In addition, observations of the small-scale structure of FTE flux tubes indicates that the velocity and magnetic field perturbations are aligned. Such a situation is expected to develop since the cross helicity, i.e., the correlation between the velocity and magnetic field, also decays less rapidly than the energy. Thus, a number of features of FTEs indicate that they were formed by a turbulent reconnection process. By extension, it appears likely that turbulent, three-dimensional reconnection may be an effective mechanism to produce flux ropes in general.