Talk abstract

Formation of a penumbra
Nazaret Bello Gonzales, Rolf Schlichenmaier, Reza Rezaei, Torsten Waldmann


We present results from a 4.5 h time series of flux emergence during the formation of a penumbra in the active region NOAA 11024. On July 1st, two bipolar pores were present in NOAA 11024. However, these pores disappeared, and on July 2nd and 3rd only faculae were visible. Two bipolar pores, somewhat further separated than on July 1st, were present (again) on July 4th. Between 8:30 UT and 13:10 UT, we observed a penumbra to form around the pore. During this period, we acquired data at the German VTT with two imaging cameras (G Band and Ca II K), and produced speckle reconstructions with KISIP (Wöger & von der Lühe 2008). Simultaneously, we observed with the 2D spectro-polarimeter GFPI scanning the Fe I 617.3 nm line with a FOV of 35"x25", and with TIP II in Fe I 1089.6 nm. With the latter we made scans covering only a FOV of 2.1''x75''. During the 4.5 h, the seeing was mostly good enough to produce speckle reconstructed images of 0.3'' or better, interrupted by one large gap of 35 minutes and a few more small gaps in the order of 10 minutes. While the dark area of the pore (later umbra) was about constant during the evolution, the final spot was 50% larger than the initial pore. Hence the magnetic flux increased during the formation process, and from the GFPI data we will be able to quantify this.