The Problem of Coronal Heating
- Centre for Plasma Astrophysics, and Leuven Mathematical Modeling and Computational Science Research Centre (LMCC), Celestijnenlaan 200B, 3001 Leuven (Belgium)
The inhomogeneous coronal plasma is a perfect environment for fast growing drift waves. The omnipresence of coronal magnetic loops implies gradients of the equilibrium plasma quantities like the density, magnetic field and temperature. These gradients are responsible for the excitation of drift waves that grow both within the two-component fluid description (both in the presence of collisions and without it) and within the two-component kinetic descriptions (due to purely kinetic effects). Some aspects of these phenomena are investigated here. In particular the analysis of the particle dynamics within the growing wave is compared with the corresponding fluid analysis. While both of them predict the stochastic heating, the threshold for the heating obtained from the single particle analysis is higher. The explanation for this effect is given. Also, the effects of the density gradient in the direction perpendicular to the magnetic field vector are investigated within the kinetic theory, in both electrostatic and electromagnetic regimes. The electromagnetic regime implies the coupling of the gradient-driven drift wave with the Alfven wave. The growth rates for the two cases are calculated and compared. It is found that, in general, the electrostatic regime is characterized by stronger growth rates, as compared with the electromagnetic perturbations. The released amount of energy density due to this heating should be more dependent on the magnitude of the background magnetic field than on the coupling of the drift and Alfven waves. The stochastic heating is expected to be much higher in regions with a stronger magnetic field. On the whole, the energy release rate caused by the stochastic heating can be several orders of magnitude above the value presently accepted as necessary for a sustainable coronal heating. The vertical stratification and the very long wavelengths along the magnetic loops imply that a drift-Alfven wave, propagating as a twisted structure along the loop, in fact occupies regions with different plasma-{beta} and, therefore, may have different (electromagnetic-electrostatic) properties, resulting in different heating rates within just one or two wavelengths.
- OSTI ID:
- 21506953
- Journal Information:
- AIP Conference Proceedings, Vol. 1306, Issue 1; Conference: Workshop on new frontiers in advanced plasma physics, Trieste (Italy), 5-16 Jul 2010; Other Information: DOI: 10.1063/1.3533189; (c) 2010 American Institute of Physics; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALFVEN WAVES
COLLISIONS
COUPLING
DENSITY
DIFFUSION
DISTURBANCES
ENERGY DENSITY
EQUILIBRIUM PLASMA
EXCITATION
FLUIDS
FOURIER ANALYSIS
HEATING RATE
MAGNETIC FIELDS
PERTURBATION THEORY
PLASMA DRIFT
POLARIZATION
STOCHASTIC PROCESSES
STRATIFICATION
WAVE PROPAGATION
WAVELENGTHS
ENERGY-LEVEL TRANSITIONS
HYDROMAGNETIC WAVES
PHYSICAL PROPERTIES
PLASMA