Effects of ion-neutral collisions on Alfv�n waves: The presence of forbidden zone and heavy damping zone

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Title:	Effects of ion-neutral collisions on Alfv�n waves: The presence of forbidden zone and heavy damping zone
Authors:	郭政靈;Weng, C. J.;Lee, L. C.;Kuo, C. L.;Wang, C. B.
Contributors:	地球科學學院太空科學與工程學系
Keywords:	70 PLASMA PHYSICS AND FUSION TECHNOLOGY;ALFVEN WAVES;APPROXIMATIONS;ASTROPHYSICS;CHROMOSPHERE;DAMPING;DISPERSION RELATIONS;MAGNETIC FIELDS;MATHEMATICAL SOLUTIONS;NEUTRAL PARTICLES;PLASMA DENSITY;VECTORS
Date:	2013-03-01
Issue Date:	2026-04-23 11:03:43 (UTC+8)
Publisher:	United States
Abstract:	摘要： Alfven waves are low-frequency transverse waves propagating in a magnetized plasma. We define the Alfven frequency {omega}{sub 0} as {omega}{sub 0}=kV{sub A}cos{theta}, where k is the wave number, V{sub A} is the Alfven speed, and {theta} is the angle between the wave vector and the ambient magnetic field. There are partially ionized plasmas in laboratory, space, and astrophysical plasma systems, such as in the solar chromosphere, interstellar clouds, and the earth ionosphere. The presence of neutral particles may modify the wave frequency and cause damping of Alfven waves. The effects on Alfven waves depend on two parameters: (1) {alpha}=n{sub n}/n{sub i}, the ratio of neutral density (n{sub n}), and ion density (n{sub i}); (2) {beta}={nu}{sub ni}/{omega}{sub 0}, the ratio of neutral collisional frequency by ions {nu}{sub ni} to the Alfven frequency {omega}{sub 0}. Most of the previous studies examined only the limiting case with a relatively large neutral collisional frequency or {beta} Much-Greater-Than 1. In the present paper, the dispersion relation for Alfven waves is solved for all values of {alpha} and {beta}. Approximate solutions in the limit {beta} Much-Greater-Than 1 as well as {beta} Much-Less-Than 1 are obtained. It is found for the first time that there is a 'forbidden zone (FZ)' in the {alpha}-{beta} parameter space, where the real frequency of Alfven waves becomes zero. We also solve the wavenumber k from the dispersion equation for a fixed frequency and find the existence of a 'heavy damping zone (HDZ).' We then examine the presence of FZ and HDZ for Alfven waves in the ionosphere and in the solar chromosphere. 出版者： United States 出版日期： 2013-03-01 出處： Physics of plasmas, 2013-03, Vol.20 (3), p.32902 資源來源： AIP Journals (American Institute of Physics) 識別號： ISSN: 1070-664X 識別號： EISSN: 1089-7674 識別號： DOI: 10.1063/1.4796043
Appears in Collections:	[DEPARTMENT OF SPACE SCIENCE AND ENGINEERING] journal & Dissertation

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