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| Paper: |
Precursor of Sunspot Penumbral Formation Discovered with Hinode SOT Observation |
| Volume: |
456, The Fifth Hinode Science Meeting |
| Page: |
43 |
| Authors: |
Shimizu, T.; Ichimoto, K.; Suematsu, Y. |
| Abstract: |
We newly found a precursory signature of sunspot penumbral formation in
Ca II H images. The precursor is a dark annular zone (width 3"-5")
around the umbra (pore), which was formed soon after the pore formation
and existed until the penumbral formation. The penumbra
was developed as if to fill the annular zone. Pre-existing ambient magnetic
field islands were moved to be distributed at the outer edge of the annular
zone and did not come into the zone. The observations indicate
that the annular zone is different from sunspot moat flow region and
that the zone is visible only in chromospheric Ca II H images,
not in photospheric G-band images. We conclude that the annular
zone reflects the formation of a magnetic canopy overlying
the region surrounding the umbra at the chromospheric level,
much before the formation of the penumbra at the photospheric level.
We can predict the region and size of the penumbra, by looking at
the appearance of dark zone around pores. |
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