Rapid rotation of a sunspot associated with flares

Abstract

Context. Active region NOAA 10424 observed on August 5, 2003 is studied in detail by using TRACE, SOHO/MDI, BBSO Hα monograph, and GOES data. This investigation focuses on the sunspot rotation and its relation with the eruptive phenomena by analyzing the magnetic configuration that the rotation results in. Aims. It is shown that there is a close relationship between the sunspot rotation and the emerging kinked magnetic Ω-loops, where the flares occur. Methods. Through tracing the traceable features motion by using the TRACE white-light images, one can get the rotation velocities of the umbra, the penumbra, the area near the penumbra, and the area far from the penumbra. Furthermore, the evolution of the emerging kinked magnetic Ω-loops and magnetic fields were studied. Results. For the sunspot with positive polarity, the umbra, the penumbra, and the area near the penumbra exhibit a conspicuous counterclockwise rotation. Moreover, the velocities decrease from the umbra through the penumbra to the area near the penumbra. It is interesting that the rotation of the umbra, the penumbra, and the area near the penumbra are opposite to that of the area far from penumbra. The rotation velocities of the umbra, the penumbra, polarity separation, and total magnetic flux increase with time. During the largest event (M1.7/Sn flare), emerging kinked magnetic Ω-loops are observed from TRACE 171 Å images. Conclusions. The different rotation speeds of the different parts of the sunspot cause twist, and then the twist is injected through the chromosphere into the corona to trigger the flares.

Multiwavelength Study of a Solar Eruption from AR NOAA 11112 I. Flux Emergence, Sunspot Rotation and Triggering of a Solar Flare

“…several hundred degrees around their umbral centers over a few days) prior to the occurrence of strong flares (Brown et al, 2003;Zhang, Li, and Song, 2007;Su et al, 2008;Yan et al, 2009;Min and Chae, 2009;Kumar, Manoharan, and Uddin, 2010a;Chandra et al, 2011). The rapid rotation of the sunspots can cause the formation of sigmoids loop that can erupt to produce flares and coronal mass ejections (Canfield, Hudson, and McKenzie, 1999;Pevtsov, 2002;Yan and Qu, 2007). The recent theories/models suggest that sunspot rotation can be caused by a pre-twisted magnetic flux tube emerging from below the photosphere (Longcope and Welsch, 2000;Gibson et al, 2004;Magara, 2006;Fan, 2009).…”

Instability of twisted magnetic tubes with axial mass flows

“…Photospheric motions may stretch and twist anchored magnetic fields, which may lead to the consequent changes in topology at higher regions. The observed rotation of sunspots (Brown et al 2003;Yan & Qu 2007) may lead to twisting of the magnetic tubes above active regions. On the other hand, the newly emerged magnetic tubes are supposed to be twisted during the rising phase through the convection zone (Moreno-Insertis & Emonet 1996;Archontis et al 2004;Murray & Hood 2008;Hood et al 2009).…”

Twisted magnetic tubes with field aligned flow

“…Photospheric motions may stretch and twist anchored magnetic fields, which may lead to the consequent changes in topology in higher regions. The observed rotation of sunspots may lead to twisting of the magnetic tubes above active regions (Brown et al 2003;Yan & Qu 2007;Kazachenko et al 2009). Also newly emerged magnetic tubes are supposed to be twisted during the rising phase through the convection zone Emonet & Moreno-Insertis 1998;Archontis et al 2004;Murray & Hood 2008;Hood et al 2009).…”