The Geometric Spreading of Coronal Plumes and Coronal Holes |
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| Authors: | Suess S T Poletto G Wang A-H Wu S T Cuseri I |
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| Institution: | (1) NASA Marshall Space Flight Center/ES82, Huntsville, AL, 35812, U.S.A;(2) Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi, 5, 50125 Firenze, Italy;(3) Department of Mechanical Engineering and Center for Space Plasma and Aeronomic Research, University of Alabama, Huntsville, AL, 35899, U.S.A;(4) Universitá di Firenze, Firenze, Italy |
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| Abstract: | The geometric spreading in plumes and in the interplume region in coronal holes is calculated, using analytic and numerical theoretical models, between 1.0 and 5.0 R . We apply a two-scale approximation that permits the rapid local spreading at the base of plumes (fl) to be evaluated separately from the global spreading (fg) imposed by coronal hole geometry. We show that fl can be computed from a potential-field model and fg can be computed from global magnetohydrodynamic simulations of coronal structure. The approximations are valid when the plasma beta is small with respect to unity and for a plume separation small with respect to a solar radius. |
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