NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Nonlinear evolution of the coronal magnetic field under reconnective relaxationRecently, Vekstein et al. (Vekstein, Priest, & Steele 1993) have developed a model for coronal heating in which the corona responds to photospheric footpoint motions by small-scale reconnection events that bring about a relaxed state while conserving magnetic helicity but not field-line connectivity. Vekstein et al. consider a partially open field configuration in which magnetic helicity is ejected to infinity on open field lines but retained in the closed-field region. Under this scheme, they describe the evolution of an initially potential field, in response to helicity injection, in the linear regime. The present work uses numerical calculations to extend the model of Vekstein et al. into the fully nonlinear regime. The results show a rise and bulging of the field lines of the closed-field region with increasing magnetic helicity, to a point where further solutions are impossible. We interpret these solution-sequence endpoints as indicating a possible loss of equilibrium, in the sense that a relaxed equilibrium state may no longer be available to the corona when sufficient helicity has been injected. The rise and bulging behavior is reminiscent of what is observed in a helmet streamer just before the start of a coronal mass ejection (CME), and so our model suggests that a catastrophic loss of magnetic equilibrium might be the initiation mechanism for CMEs. We also find that some choices of boundary conditions can result in qualitative changes in the magnetic topology, with the appearance of magnetic islands. Whether or not this behavior occurs depends on the relative strengths of the fields in the closed- and open-field regions; in particular, island formation is most likely when the open field (which is potential) is strong and thus acts to confine the force-free closed field. Finally, we show that the energy released through reconnective relaxation can be a substantial fraction of the magnetic energy injected into the corona through footpoint motions and may be sufficient for heating the corona above active regions.
Document ID
19950048310
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Wolfson, R.
(University of St. Andrews St. Andrews, United Kingdom)
Vekstein, G. E.
(University of St. Andrews St. Andrews, United Kingdom)
Priest, E. R.
(University of St. Andrews St. Andrews, United Kingdom)
Date Acquired
August 16, 2013
Publication Date
June 10, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 428
Issue: 1
ISSN: 0004-637X
Subject Category
Solar Physics
Accession Number
95A79909
Funding Number(s)
CONTRACT_GRANT: NAGW-2141
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available