Heating and cooling at a coronal magnetic null
File(s)null_cooling.pdf (1.48 MB)
Published version
Author(s)
Cargill, PJ
Hood, AW
Johnson, D
Type
Journal Article
Abstract
Conductive cooling of the solar corona at a magnetic null is examined. An initial equilibrium is set up, balancing thermal conduction and a constant spatially uniform coronal heating. The heating is then turned off and the subsequent conductive cooling calculated. An equation for the cooling is obtained using the method of separation of variables and it is shown that the equations for the equilibrium between conduction and heating, and the time-dependent cooling are mathematically identical with a simple change of variables. Thus, the properties of the cooling phase are automatically determined by the equilibrium state. For a two-dimensional null, the characteristic cooling time-scale increases over that in a straight field by a factor of between 2 and 5, with a scaling determined by the ratio of the average and base areas of a flux element. There is no explicit dependence on the very large areas that can arise near the null.
Date Issued
2025-10-01
Date Acceptance
2025-08-27
Citation
Monthly Notices of the Royal Astronomical Society, 2025, 542 (4), pp.3385-3394
ISSN
0035-8711
Publisher
Oxford University Press
Start Page
3385
End Page
3394
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
542
Issue
4
Copyright Statement
© The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Subjects
ACTIVE-REGION
Astronomy & Astrophysics
conduction
Physical Sciences
PLASMAS
Science & Technology
Sun: corona
Sun: magnetic fields
Publication Status
Published
Date Publish Online
2025-09-02