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| Paper: |
Evershed Flows along Penumbral Flux Tubes in Sunspots |
| Volume: |
354, Solar MHD Theory and Observations: A High Spatial Resolution Perspective |
| Page: |
224 |
| Authors: |
Thomas, J.H. |
| Abstract: |
Theoretical models of the Evershed flow in a sunspot based on the thin flux tube approximation are compared. The super-Alfvénic, “sea-serpent” flow configurations found by Schlichenmaier (2002, 2003) are shown to be gravitationally unstable. If indeed super-Alfvénic flow speeds can be achieved along penumbral flux tubes, any undulations that occur will form preferentially in a horizontal plane and hence will not explain the observed Evershed downflows or outward-moving penumbral grains. On the other hand, sub-Alfvénic, arched flow configurations, such as the siphon-flow models of Montesinos and Thomas (1997), are gravitationally stable. The outer part of a siphon-flow flux tube is submerged, in opposition to its magnetic buoyancy, by downward magnetic flux pumping in the granular convective layer outside the sunspot. |
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