AAS 204th Meeting, June 2004
Session 88 Solar Photosphere and Below
SPD Oral, Thursday, June 3, 2004, 10:30-11:30am, 702

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[88.04] G-band Images from MHD Convection Simulations

R. F. Stein (Michigan State University), M. Carlsson (University of Oslo, Norway), A Nordlund (Astronomical Obsrvatroy, NBIfAFG, Denmark), G. Scharmer (Royal Swedish Academy of Sciences, Sweden)

High resolution magneto-convection simulations are used to calculate G-band and G-continuum images at various angles. Towards the limb the simulations show "hilly" granulation, bright granulation walls, intergranular striations and "sticking out" G-band bright features similar to observations. The increased brightness in magnetic elements is due to their lower density compared with the surrounding intergranular medium, so that one sees deeper layers where the temperature is higher. At a given geometric height, the magnetic elements are not hotter 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. At large angles, the deep lying magnetic elements are hidden by the granules and the bright points are no longer visible. Where the "magnetic valleys" are aligned with the line of sight, they are visible as elongated structures seemingly "sticking out". Even when the deep hot surface is hidden, the low density in the strong magnetic elements causes unit line-of-sight optical depth to occur deeper in the granule walls behind then for rays not going through magnetic elements. Flux concentrations in intergranular lanes therefore cause a striped intensity pattern. This work is funded by NSF grants AST 0205500 and ATM 99881112 and NASA grants NAG 5 12450 and NNGO4GB92G.

The author(s) of this abstract have provided an email address for comments about the abstract: stein@pa.msu.edu

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