WKB estimates for the onset of ideal MHD instabilities in solar coronal loops期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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WKB estimates for the onset of ideal MHD instabilities in solar coronal loops

Authors:	A W Hood P De Bruyne R A M Van Der Linden M Goossens

Institution:	(1) Department of Mathematical and Computational Sciences, University of St. Andrews, KY16 9SS, UK;(2) LABORELEC, B-1630 Linkebeek, Belgium;(3) Department of Mathematical and Computational Sciences, University of St. Andrews, KY16 9SS, UK;(4) Centrum voor Plasma Astrofysica, B-3001 Leuven, Belgium

Abstract:	A WKB approach, based on the method of Connor, Hastie, and Taylor (1979), is used to obtain simple estimates of the critical conditions for the onset of ideal MHD instabilities in line-tied solar coronal loops. The method is illustrated for the constant twist, Gold-Hoyle (1960) field, and the critical conditions are compared with previous and new numerical results. For the force-free case, the WKB estimate for the critical loop length reduces to $2\pi m + \sqrt 2 \pi$ . For the sufficiently non-force-free case the critical length can be expressed in the forml ₀ +l ₁/m. The results confirm the findings of De Bruyne and Hood (1992) that for force-free fields them = 1 mode is the first mode to become unstable but for the sufficiently strong non-force-free case this reverses with them → ∞ mode being excited first.

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