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Title: The Heating of Solar Coronal Loops by Alfvén Wave Turbulence

Abstract

In this paper we further develop a model for the heating of coronal loops by Alfvén wave turbulence (AWT). The Alfvén waves are assumed to be launched from a collection of kilogauss flux tubes in the photosphere at the two ends of the loop. Using a three-dimensional magnetohydrodynamic model for an active-region loop, we investigate how the waves from neighboring flux tubes interact in the chromosphere and corona. For a particular combination of model parameters we find that AWT can produce enough heat to maintain a peak temperature of about 2.5 MK, somewhat lower than the temperatures of 3–4 MK observed in the cores of active regions. The heating rates vary strongly in space and time, but the simulated heating events have durations less than 1 minute and are unlikely to reproduce the observed broad differential emission measure distributions of active regions. The simulated spectral line nonthermal widths are predicted to be about 27 km s{sup −1}, which is high compared to the observed values. Therefore, the present AWT model does not satisfy the observational constraints. An alternative “magnetic braiding” model is considered in which the coronal field lines are subject to slow random footpoint motions, but we find thatmore » such long-period motions produce much less heating than the shorter-period waves launched within the flux tubes. We discuss several possibilities for resolving the problem of producing sufficiently hot loops in active regions.« less

Authors:
 [1]; ;  [2]
  1. 5001 Riverwood Avenue, Sarasota, FL 34231 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22679710
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 849; 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; CHROMOSPHERE; COMPARATIVE EVALUATIONS; DISTRIBUTION; EMISSION; HEAT; HEATING RATE; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PHOTOSPHERE; RANDOMNESS; SIMULATION; SOLAR CORONA; SPACE; SUN; THREE-DIMENSIONAL CALCULATIONS; TURBULENCE

Citation Formats

Van Ballegooijen, A. A., Asgari-Targhi, M., and Voss, A.. The Heating of Solar Coronal Loops by Alfvén Wave Turbulence. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA9118.
Van Ballegooijen, A. A., Asgari-Targhi, M., & Voss, A.. The Heating of Solar Coronal Loops by Alfvén Wave Turbulence. United States. doi:10.3847/1538-4357/AA9118.
Van Ballegooijen, A. A., Asgari-Targhi, M., and Voss, A.. Wed . "The Heating of Solar Coronal Loops by Alfvén Wave Turbulence". United States. doi:10.3847/1538-4357/AA9118.
@article{osti_22679710,
title = {The Heating of Solar Coronal Loops by Alfvén Wave Turbulence},
author = {Van Ballegooijen, A. A. and Asgari-Targhi, M. and Voss, A.},
abstractNote = {In this paper we further develop a model for the heating of coronal loops by Alfvén wave turbulence (AWT). The Alfvén waves are assumed to be launched from a collection of kilogauss flux tubes in the photosphere at the two ends of the loop. Using a three-dimensional magnetohydrodynamic model for an active-region loop, we investigate how the waves from neighboring flux tubes interact in the chromosphere and corona. For a particular combination of model parameters we find that AWT can produce enough heat to maintain a peak temperature of about 2.5 MK, somewhat lower than the temperatures of 3–4 MK observed in the cores of active regions. The heating rates vary strongly in space and time, but the simulated heating events have durations less than 1 minute and are unlikely to reproduce the observed broad differential emission measure distributions of active regions. The simulated spectral line nonthermal widths are predicted to be about 27 km s{sup −1}, which is high compared to the observed values. Therefore, the present AWT model does not satisfy the observational constraints. An alternative “magnetic braiding” model is considered in which the coronal field lines are subject to slow random footpoint motions, but we find that such long-period motions produce much less heating than the shorter-period waves launched within the flux tubes. We discuss several possibilities for resolving the problem of producing sufficiently hot loops in active regions.},
doi = {10.3847/1538-4357/AA9118},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 849,
place = {United States},
year = {2017},
month = {11}
}