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Title: On the relationship between photospheric footpoint motions and coronal heating in solar active regions

Abstract

Coronal heating theories can be classified as either direct current (DC) or alternating current (AC) mechanisms, depending on whether the coronal magnetic field responds quasi-statically or dynamically to the photospheric footpoint motions. In this paper we investigate whether photospheric footpoint motions with velocities of 1-2 km s{sup –1} can heat the corona in active regions, and whether the corona responds quasi-statically or dynamically to such motions (DC versus AC heating). We construct three-dimensional magnetohydrodynamic models for the Alfvén waves and quasi-static perturbations generated within a coronal loop. We find that in models where the effects of the lower atmosphere are neglected, the corona responds quasi-statically to the footpoint motions (DC heating), but the energy flux into the corona is too low compared to observational requirements. In more realistic models that include the lower atmosphere, the corona responds more dynamically to the footpoint motions (AC heating) and the predicted heating rates due to Alfvén wave turbulence are sufficient to explain the observed hot loops. The higher heating rates are due to the amplification of Alfvén waves in the lower atmosphere. We conclude that magnetic braiding is a highly dynamic process.

Authors:
;  [1];  [2]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS-15, Cambridge, MA 02138 (United States)
  2. SECAM, University of Exeter, EX4 4QF (United Kingdom)
Publication Date:
OSTI Identifier:
22356818
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 787; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; ALTERNATING CURRENT; AMPLIFICATION; ATMOSPHERES; COMPARATIVE EVALUATIONS; DIRECT CURRENT; DISTURBANCES; HEATING RATE; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PERTURBATION THEORY; SUN; TURBULENCE

Citation Formats

Van Ballegooijen, A. A., Asgari-Targhi, M., and Berger, M. A. On the relationship between photospheric footpoint motions and coronal heating in solar active regions. United States: N. p., 2014. Web. doi:10.1088/0004-637X/787/1/87.
Van Ballegooijen, A. A., Asgari-Targhi, M., & Berger, M. A. On the relationship between photospheric footpoint motions and coronal heating in solar active regions. United States. https://doi.org/10.1088/0004-637X/787/1/87
Van Ballegooijen, A. A., Asgari-Targhi, M., and Berger, M. A. 2014. "On the relationship between photospheric footpoint motions and coronal heating in solar active regions". United States. https://doi.org/10.1088/0004-637X/787/1/87.
@article{osti_22356818,
title = {On the relationship between photospheric footpoint motions and coronal heating in solar active regions},
author = {Van Ballegooijen, A. A. and Asgari-Targhi, M. and Berger, M. A.},
abstractNote = {Coronal heating theories can be classified as either direct current (DC) or alternating current (AC) mechanisms, depending on whether the coronal magnetic field responds quasi-statically or dynamically to the photospheric footpoint motions. In this paper we investigate whether photospheric footpoint motions with velocities of 1-2 km s{sup –1} can heat the corona in active regions, and whether the corona responds quasi-statically or dynamically to such motions (DC versus AC heating). We construct three-dimensional magnetohydrodynamic models for the Alfvén waves and quasi-static perturbations generated within a coronal loop. We find that in models where the effects of the lower atmosphere are neglected, the corona responds quasi-statically to the footpoint motions (DC heating), but the energy flux into the corona is too low compared to observational requirements. In more realistic models that include the lower atmosphere, the corona responds more dynamically to the footpoint motions (AC heating) and the predicted heating rates due to Alfvén wave turbulence are sufficient to explain the observed hot loops. The higher heating rates are due to the amplification of Alfvén waves in the lower atmosphere. We conclude that magnetic braiding is a highly dynamic process.},
doi = {10.1088/0004-637X/787/1/87},
url = {https://www.osti.gov/biblio/22356818}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 787,
place = {United States},
year = {Tue May 20 00:00:00 EDT 2014},
month = {Tue May 20 00:00:00 EDT 2014}
}