KINETIC INSTABILITY OF DRIFT-ALFVEN WAVES IN SOLAR CORONA AND STOCHASTIC HEATING
- Center for Plasma Astrophysics, K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium)
The solar atmosphere is structured and inhomogeneous, both horizontally and vertically. The omnipresence of coronal magnetic loops implies gradients of the equilibrium plasma quantities such as 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). In this work, the effects of the density gradient in the direction perpendicular to the magnetic field vector are investigated within the kinetic theory, in both electrostatic (ES) and electromagnetic (EM) regimes. The EM 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 ES regime is characterized by stronger growth rates, as compared with the EM perturbations. Also discussed is the stochastic heating associated with the drift wave. 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 (EM-ES) properties, resulting in different heating rates within just one or two wavelengths.
- OSTI ID:
- 21457091
- Journal Information:
- Astrophysical Journal, Vol. 719, Issue 2; Other Information: DOI: 10.1088/0004-637X/719/2/1335; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ALFVEN WAVES
ENERGY DENSITY
EQUILIBRIUM PLASMA
MAGNETIC FIELDS
PERTURBATION THEORY
SOLAR CORONA
STOCHASTIC PROCESSES
SUN
WAVE PROPAGATION
ATMOSPHERES
HYDROMAGNETIC WAVES
MAIN SEQUENCE STARS
PLASMA
SOLAR ATMOSPHERE
STARS
STELLAR ATMOSPHERES
STELLAR CORONAE