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High resolution limb images synthesized from 3D MHD simulations

Published online by Cambridge University Press:  14 March 2005

Mats Carlsson
Affiliation:
Institute of Theoretical Astrophysics, University of Oslo, Norway Also at Center of Mathematics for Applications, University of Oslo, P.O. Box 1053 Blindern Blindern PBf N-0316 Oslo, Norway.
Robert F. Stein
Affiliation:
Dept. of Physics and Astronomy, Michigan State University, East Lansing, USA
Åke Nordlund
Affiliation:
NBIfAFG, University of Copenhagen, Denmark
Göran B. Scharmer
Affiliation:
The Institute for Solar Physics of the Royal Swedish Academy of Sciences, Stockholm, Sweden
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Abstract

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We present the first center-to-limb G-band images synthesized from high resolution simulations of solar magneto-convection. Towards the limb the simulations show “hilly” granulation with dark bands on the far side, bright granulation walls and striated faculae, similar to observations. At disk center G-band bright points are flanked by dark lanes. The increased brightness in magnetic elements is due to their lower density compared with the surrounding intergranular medium. One thus sees deeper layers where the temperature is higher. At a given geometric height, the magnetic elements are cooler than the surrounding medium. In the G-band, the contrast is further increased by the destruction of CH in the low density magnetic elements. The optical depth unity surface is very corrugated. Bright granules have their continuum optical depth unity 80 km above the mean surface, the magnetic elements 200-300 km below. The horizontal temperature gradient is especially large next to flux concentrations. When viewed at an angle, the deep magnetic elements optical surface is hidden by the granules and the bright points are no longer visible, except where the “magnetic valleys” are aligned with the line of sight. Towards the limb, the low density in the strong magnetic elements causes unit line-of-sight optical depth to occur deeper in the granule walls behind than for rays not going through magnetic elements and variations in the field strength produce a striated appearance in the bright granule walls.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Type
Contributed Papers
Copyright
© 2004 International Astronomical Union