Sunspot penumbra
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Formation of a sunspot penumbra in Ca II K (2/2)
Vacuum Tower Telescope (VTT)
The penumbra of sunspots is a magnetized region where convective motions are not entirely inhibited. Understanding its structure, brightness, and dynamics represents a challenge, as our ability to make progress depends on improvements in the spatial resolution of the observations.
The movie shows the formation of a sunspot penumbra over the course of 4.5 hours as recorded through a Ca II K filter at the Vacuum Tower Telescope (Observatorio del Teide, Tenerife, Spain) on 2009 July 4. This is an extremely difficult process to catch, since we still do not know when a naked pore will develop a penumbra. The Ca II K observations monitor the upper photosphere/lower chromosphere (see the accompanying G-band movie for the photosphere). The movie show that the penumbra grows in sectors, out of a naked pore, on the external side of the active region where flux emergence is not very intense.
To download the movie, click HERE
Movie credit: Schlichenmaier, Rezaei, Bello Gonzalez, & Waldmann, 2010, Astronomy and Astrophysics, 512, L1