Twisted Flux Ropes in the Solar Corona

  1. C. T. Russell,
  2. E. R. Priest and
  3. L. C. Lee
  1. P. K. Browning

Published Online: 21 MAR 2013

DOI: 10.1029/GM058p0219

Physics of Magnetic Flux Ropes

Physics of Magnetic Flux Ropes

How to Cite

Browning, P. K. (1990) Twisted Flux Ropes in the Solar Corona, 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/GM058p0219

Author Information

  1. Department of Pure and Applied Physics, Umist, P.O. Box 88, Manchester M60 1QD, England

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1990

ISBN Information

Print ISBN: 9780875900261

Online ISBN: 9781118663868

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Keywords:

  • Solar photosphere;
  • Magnetic flux;
  • Astrophysics

Summary

Loop structures, which are essentially magnetic flux tubes, often with twist, are common in the solar corona. This paper considers the magnetic equilibrium of twisted coronal loops. Ignoring curvature, as a loop is twisted at the photospheric footpoints, longitudinal structure develops with the centre of the loop tending to expand radially. Results of a 2D numerical code show that nearly all of the expansion occurs in narrow boundary layers near the photosphere, and most of the loop is approximately a straight cylinder. If a small amount of dissipation is allowed, the field relaxes to a minimum energy state × B = μB. In the limit of immediate relaxation, the loop evolves through a sequence of such states; the loop surface is free, the radius being determined by pressure balance and flux conservation. A critical point is reached if the loop is strongly twisted, whereby the local current μ = μoj/B cannot be further increased. The heating vanishes in this immediate relaxation limit, but for finite relaxation times sufficient energy can be dissipated to heat the corona.