Heating of the Solar Chromosphere and Corona by Alfvén Wave Turbulence

A three-dimensional magnetohydrodynamic (MHD) model for the propagation and dissipation of Alfven waves in a coronal loop is developed. The model includes the lower atmospheres at the two ends of the loop. The waves originate on small spatial scales (less than 100 km) inside the kilogauss flux eleme...

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Bibliographic Details
Published in:The Astrophysical journal 2011-07, Vol.736 (1), p.3-jQuery1323905833864='48'
Main Authors: van Ballegooijen, A. A, Asgari-Targhi, M, Cranmer, S. R, DeLuca, E. E
Format: Article
Language:English
Subjects:
ALFVEN WAVES
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ATMOSPHERES
CHROMOSPHERE
FLUID MECHANICS
HEATING
HYDRODYNAMICS
HYDROMAGNETIC WAVES
MAGNETISM
MAGNETOHYDRODYNAMICS
MECHANICS
SIMULATION
SOLAR ATMOSPHERE
SOLAR CORONA
STELLAR ATMOSPHERES
STELLAR CORONAE
THREE-DIMENSIONAL CALCULATIONS
TURBULENCE
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Summary:A three-dimensional magnetohydrodynamic (MHD) model for the propagation and dissipation of Alfven waves in a coronal loop is developed. The model includes the lower atmospheres at the two ends of the loop. The waves originate on small spatial scales (less than 100 km) inside the kilogauss flux elements in the photosphere. The model describes the nonlinear interactions between Alfven waves using the reduced MHD approximation. The increase of Alfven speed with height in the chromosphere and transition region (TR) causes strong wave reflection, which leads to counter-propagating waves and turbulence in the photospheric and chromospheric parts of the flux tube. Part of the wave energy is transmitted through the TR and produces turbulence in the corona. We find that the hot coronal loops typically found in active regions can be explained in terms of Alfven wave turbulence, provided that the small-scale footpoint motions have velocities of 1-2 km s--1 and timescales of 60-200 s. The heating rate per unit volume in the chromosphere is two to three orders of magnitude larger than that in the corona. We construct a series of models with different values of the model parameters, and find that the coronal heating rate increases with coronal field strength and decreases with loop length. We conclude that coronal loops and the underlying chromosphere may both be heated by Alfvenic turbulence.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/736/1/3