Coronal disturbances |
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Authors: | W. J. Wagner |
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Affiliation: | (1) Space Science Lab., ES-52, NASA/Marshall Space Flight Center, 35812 Huntsville, AL, U.S.A.;(2) Dept. of Mechanical Engineering, University of Alabama in Huntsville, 35812 Huntsville, AL, U.S.A.;(3) Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, 35812 Huntsville, AL, U.S.A. |
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Abstract: | We have studied chromospheric mass injection into an overlying coronal dipole magnetic field using a 2-D ideal magnetohydrodynamic (MHD) numerical model. The results indicate that such injection can produce magnetic field deformation conducive to active region prominences - namely, Kippenhahn-Schlüter (K-S) type configurations for stable support of injected plasma. We show the optimum conditions for such dynamical formation of K-S-type field configurations.Observations show that an active region prominence formation is preceded by the accumulation of absorptive strands above a neutral line. We hypothesize that an absorptive strand is formed by a chromospheric asymmetric mass injection into the overlying coronal magnetic field and that a necessary condition for the accumulation of the strands is that the mass injection forms a K-S-type field configuration. The results of our numerical simulation of the injection dynamics support our hypothesis. To form a K-S-type magnetic field configuration, we find that a narrow range of injection density, velocity, and magnetic field strength must be used; spicule-like, asymmetric mass injection seems favorable.The limited parameter range that exists for the formation of K-S-type magnetic field configurations in asymmetric injections may explain why active region prominences do not form everywhere on every neutral line. |
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