Observational manifestations of solar magnetoconvection:: Center-to-limb variation

被引:152
作者
Carlsson, M
Stein, RF
Nordlund, Å
Scharmer, GB
机构
[1] Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway
[2] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[3] Univ Copenhagen, Niels Bohr Inst Astron Phys & Geophys, DK-2100 Copenhagen, Denmark
[4] Royal Swedish Acad Sci, Inst Solar Phys, Alba Nova Univ Ctr, SE-10691 Stockholm, Sweden
基金
美国国家航空航天局;
关键词
convection; magnetic fields; MHD; Sun; faculae; plages; Sun : photosphere;
D O I
10.1086/423305
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present the first center-to-limb G-band images synthesized from high-resolution simulations of solar magnetoconvection. Toward 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. Toward 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.
引用
收藏
页码:L137 / L140
页数:4
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