Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2009-05-06
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
13 pages, 7 figures. To appear in "Magnetic Coupling between the Interior and the Atmosphere of the Sun", eds. S.S. Hasan and
Scientific paper
Numerical simulations have by now revealed that the fine scale structure of the penumbra in general and the Evershed effect in particular is due to overturning convection, mainly confined to gaps with strongly reduced magnetic field strength. The Evershed flow is the radial component of the overturning convective flow visible at the surface. It is directed outwards -- away from the umbra -- because of the broken symmetry due to the inclined magnetic field. The dark penumbral filament cores visible at high resolution are caused by the 'cusps' in the magnetic field that form above the gaps. Still remaining to be established are the details of what determines the average luminosity of penumbrae, the widths, lengths, and filling factors of penumbral filaments, and the amplitudes and filling factors of the Evershed flow. These are likely to depend at least partially also on numerical aspects such as limited resolution and model size, but mainly on physical properties that have not yet been adequately determined or calibrated, such as the plasma beta profile inside sunspots at depth and its horizontal profile, the entropy of ascending flows in the penumbra, etc.
Nordlund Aake
Scharmer Goeran B.
No associations
LandOfFree
Convection and the Origin of Evershed Flows does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Convection and the Origin of Evershed Flows, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Convection and the Origin of Evershed Flows will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-455045