Magnetic and boundary effects on thermal instabilities in solar magnetic fields: Localized modes in a slab geometry |
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| Authors: | P J Cargill A W Hood |
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| Institution: | (1) Department of Mathematical Sciences, University of St. Andrews, KY16 9SS Fife, Scotland;(2) Present address: Department of Physics and Astronomy, University of Maryland, 20742 College Park, MD, U.S.A. |
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| Abstract: | The coupling of thermal and ideal MHD effects in a sheared magnetic field is investigated. A slab geometry is considered so that the Alfvén mode can be decoupled from the system. With the total perturbed pressure approximately zero, the fast mode is eliminated and a system of linearized equations describing magnetic effects on the slow mode and thermal mode is derived. These modes evolve independently on individual fieldlines. One of the main features of this approach is that the influence of the dense photosphere can be included. A variety of different conditions that simulate the photospheric boundary are presented and the different results are discussed. A choice of field geometry and boundary conditions is made which removes mode rational surfaces so that there are no regions in which parallel thermal conduction can be neglected. This provides a stabilizing mechanism for the thermal mode. Growth rates are reduced by 30–40% and there is complete stabilization for sufficiently short fieldlines. The influence of dynamic and thermal boundary conditions on the formation of prominences is discussed. |
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