Origins of Coronal Energy and Helicity in NOAA 10030

Abstract

Exploring the origins of coronal helicity and energy, as well as determining the mechanisms that lead to coronal energy release, is a fundamental topic in solar physics. Using MDI 96 minute line-of-sight and HSOS vector magnetograms in conjunction with TRACE white-light and UV (1600 ?) images and BBSO H? and SOHO EIT (195 ?) images, we find in active region NOAA 10030 that a large positive polarity sunspot, located in the center of the region, exhibited significant counterclockwise rotation, which continued for 6 days during the period 2002 July 12-18. This rotating sunspot was related to the formation of inverse-$t{S}$ -->-shaped filaments, left-handed twist of the vector magnetic fields, and the production of strong negative vertical current, but exhibited little emergence of magnetic flux. In all, five M-class and two X-class flares were produced around this rotating sunspot over the 6 day period. The observed characteristics of the strongly rotating sunspot suggest that sunspots can undergo strong intrinsic rotation, the source of which may originate below the photosphere and can play a significant role in helicity production and injection and energy buildup in the corona. A sunspot with negative magnetic polarity showed fast and significant emergence in the eastern portion of the active region, and moved northeastward over several days, but exhibited little rotation. The moving sunspot also exhibited the formation of inverse-$t{S}$ -->-shaped filaments, left-handed twist of vector magnetic fields and coronal structure, and the production of stronger positive current. The observed characteristics of the emerging sunspot suggest that significant emergence of twisted magnetic fields may not always result in the rotation of the associated sunspots, but they do play a very important role in the coronal helicity accumulation and free-energy build-up.