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| Paper: |
On the Formation of Penumbrae as Observed with the German VTT,
SOHO/MDI, and SDO/HMI |
| Volume: |
455, 4th Hinode Science Meeting: Unsolved Problems and Recent Insights |
| Page: |
61 |
| Authors: |
Schlichenmaier, R.; Rezaei, R.; González, N. B. |
| Abstract: |
Solar magnetic fields are generated in the solar interior and pop up
at the solar surface to form active regions. As the magnetic field
appears on the surface, it forms various structures like small
magnetic elements, pores, and sunspots. The nature of these formation
processes is largely unknown. In this contribution we elaborate on the
formation of sunspots and particularly on the formation of
penumbrae. We report on observations that we obtained at the German
Vacuum Tower Telescope (VTT) on July 4, 2009 on the formation of the
spot in AR 11024. This data set is complemented with data from the
Michelson Doppler Imager (MDI) aboard SOHO, which offers an entire
time coverage. Moreover, the evolution of AR 11024 is compared with a
particular event of penumbra formation in AR 11124 around November 13,
2010, using intensity images from the Helioseismic and Magnetic Imager
(HMI) onboard SDO. We conclude that two processes contribute to the
increase of the magnetic flux of a sunspot: (1) merging pores, and (2)
emerging bipoles of which the spot polarity migrates towards and
merges with the spot. As the penumbra forms, the area, magnetic flux,
and maximum field strength in the umbra stay constant or increase
slightly, i.e., the formation of the penumbra is associated with flux
emergence and flux increase of the proto-spot. If two pores merge
or if a pore merges with a proto-spot a light bridge is created. This
initial light bridge dissolves in the further evolution. |
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