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Sunspots and the physics of magnetic flux tubes. I. The general nature of the sunspots.

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Abstract

Analysis of the dynamical stability of a large flux tube suggests that the field of a sunspot must divide into many separate tubes within the first 1000 km below the surface. Buoyancy of the Wilson depression at the visible surface and probably also a downdraft beneath the sunspot hold the separate tubes in a loose cluster. Convective generation of Alfven waves, which are emitted preferentially downward, cools the tubes. Aerodynamic drag on a slender flux tube stretched vertically across a convective cell is also studied. Since the drag is approximately proportional to the local kinetic energy density, the density stratification weights the drag in favor of the upper layers. Horizontal motions concentrated in the bottom of the convective cell may reverse this density effect. A downdraft of about two km/sec through the flux tubes beneath the sunspot is hypothesized.


Publication:

The Astrophysical Journal

Pub Date:
June 1979
DOI:

10.1086/157150

Bibcode:
1979ApJ...230..905P
Keywords:
  • Aerodynamic Drag;
  • Dynamic Stability;
  • Magnetic Field Configurations;
  • Magnetic Flux;
  • Sunspots;
  • Asymmetry;
  • Convective Flow;
  • Fluid Dynamics;
  • Magnetohydrodynamic Waves;
  • Magnetohydrodynamics;
  • Qualitative Analysis;
  • Solar Physics;
  • Standing Waves;
  • Vertical Motion;
  • Solar Physics;
  • Magnetic Fields:Sunspots;
  • Sunspots:Stability;
  • Sunspots:Structure