Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-20T03:38:36.999Z Has data issue: false hasContentIssue false
  • English
  • Français

A physical description of magnetic helicity evolution in the presence of reconnection lines

Published online by Cambridge University Press:  13 March 2009

Andrew N. Wright  and
Mitchell A. Berger
Andrew N. Wright
Affiliation:
Astronomy Unit, School of Mathematical Sciences, Queen Mary and Westfield College, London El 4NS, England
Mitchell A. Berger
Affiliation:
Department of Mathematics, University College London, 25 Gordon Street, London WC1E 6BT, England
Get access Rights & Permissions [Opens in a new window]

Abstract

The dissipation of relative magnetic helicity due to the presence of a resistive reconnection region is considered. We show that when the reconnection region has a vanishing cross-section, helicity is conserved, in agreement with previous studies. It is also shown that in two-dimensional systems reconnection can produce highly twisted reconnected flux tubes. Reconnection at a high magnetic Reynolds number generally conserves helicity to a good approximation. However, reconnection with a small Reynolds number can produce significant dissipation of helicity. We prove that helicity dissipation in two-dimensional configurations is associated with the retention of some of the inflowing magnetic flux by the reconnection region, vr. When the reconnection site is a simple Ohmic conductor, all of the magnetic field parallel to the reconnection line that is swept into vr is retained. (In contrast, the inflowing magnetic field perpendicular to the line is annihilated.) We are able to relate the amount of helicity dissipation to the retained flux. A physical interpretation of helicity dissipation is developed by considering the diffusion of magnetic field lines through vr. When compared with helicity-conserving reconnection, the two halves of a reconnected flux sheet appear to have slipped relative to each other parallel to the reconnection line. This provides a useful method by which the reconnected field geometry can be constructed: the incoming flux sheets are ‘cut’ where they encounter vr, allowed to slip relative to each other, and then ‘pasted’ together to form the reconnected flux sheets. This simple model yields estimates for helicity dissipation and the flux retained by vr in terms of the amount of slippage. These estimates are in agreement with those expected from the governing laws.

Type
Research Article
Information
Journal of Plasma Physics , Volume 46 , Issue 1 , August 1991 , pp. 179 - 199
Copyright
Copyright © Cambridge University Press 1991

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Barnes, C. W., Fernandez, J. C, Henins, I., Hoida, H. W., Jabbe, T. R., Knox, S. O., Marklin, G. J. & McKenna, K. S. 1986 Phys. Fluids 29, 3415.CrossRefGoogle Scholar
Berger, M. A. 1984 Geophys. Astrophys. Fluid Dyn. 30, 79.CrossRefGoogle Scholar
Berger, M. A. 1988 Reconnection in Space Plasma (ed. Guyenne, T. D. & Hunt, J. J.), p. 83. ESA SP-285, vol. 2.Google Scholar
Berger, M. A. & Field, G. B. 1984 J. Fluid Mech. 147, 133.CrossRefGoogle Scholar
Biernat, H. K., Heyn, M. F. & Semenov, V. S. 1987 J. Geophys. Res. 92, 3392.Google Scholar
Browning, P. K. 1988a J. Plasma Phys. 40, 263.Google Scholar
Browning, P. K. 1988b Plasma Phys. Contr. Fusion 30, 1.CrossRefGoogle Scholar
Cowley, S. W. H. 1985 Solar System Magnetic Fields (ed. Priest, E. R.), p. 121. Reidel.CrossRefGoogle Scholar
Dungey, J. W. 1961 Phys. Rev. Lett. 6, 47.CrossRefGoogle Scholar
Finn, J. H. & Antonsen, T. M. 1985 Comments Plasma Phys. Contr. Fusion 9, 111.Google Scholar
Fu, Z. F. & Lee, L. C. 1986 J. Geophys. Res. 91, 13373.Google Scholar
Hesse, M. & Schindler, K. 1988 J. Geophys. Res. 93, 5559.Google Scholar
Heyvaerts, J. & Priest, E. R. 1984 Astron. Astrophys. 137, 63.Google Scholar
Jensen, T. H. & Chu, M. S. 1984 Phys. Fluids 27, 281.CrossRefGoogle Scholar
Priest, E. R. 1985 Rep. Prog. Phys. 48, 955.CrossRefGoogle Scholar
Song, Y. & Lysak, R. L. 1989 J. Geophys. Res. 94, 5273.Google Scholar
Taylor, J. B. 1974 Phys. Rev. Lett. 33, 1139.Google Scholar
Taylor, J. B. 1986 Rev. Mod. Phys. 58, 741.CrossRefGoogle Scholar
Wright, A. N. 1987 Planet. Space Sci. 35, 813.Google Scholar
Wright, A. N. & Berger, M. A. 1989 J. Geoxsphys. Res. 94, 1295.CrossRefGoogle Scholar
Wright, A. N. & Berger, M. A. 1990 J. Geophys. Res. 95, 8029.CrossRefGoogle Scholar