Relationship between rotating sunspots and flare productivity

Abstract

To understand both the effects of dynamo and the nature of flaring activity, we identified rotating sunspots and then classified them into six types by using the data of Transition Region and Coronal Explorer and Solar and Heliospheric Observatory/Michelson Doppler Imager in Solar Cycle 23. The classification is made by their rotating directions and relative positions (leading or following sunspots), while the corresponding samples are given. The statistics of flares relevant to these sunspots are presented to show the relationship between different types of rotating sunspots and their flare productivity. It is found that some types of rotating sunspots are in favour of producing flares, and, outstandingly those active regions with sunspots of rotating direction opposite to the differential rotation have much higher strong (X-class) flare productivity. Furthermore, we found that the ratio of the number of flares defined in this paper is inconsistent to the number evolution of the six types of rotating sunspots. The maximum ratios of the six types except type VI appear after the maximum year. Additionally, there are total 60 possible patterns of rotating sunspots belonging to the six types, among which 35 patterns are found but 25 patterns remain to be discovered in other solar cycles. These results not only place further constraints on the dynamo theory but also reveal that the rotation motions of sunspots can be greatly helpful to the energy buildup of solar flares.

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

“…We believe that here we have a superposition of a flux rope emerging with negative helicity (as shown by the magnetic tongue/tails structure, and a smaller rotation of the flux rope as a whole). Yan, Qu, and Kong (2008) proposed that the two sunspots with the same rotating direction have higher flare productivity than those with opposite rotating directions, and this scenario makes it easier to store magnetic energy and increase the helicity of the flux tube. Indeed, the present AR was not large flare/CME productive and the first flare (M2.9) was observed on 16 October 2010 associated with a slow CME (speed≈350 km s −1 ).…”

Rotation of sunspots in active region NOAA 10930

“…In particular, it was found that the twist of the EUV loop structure in the corona is caused by the sunspot rotation (Brown et al, 2001(Brown et al, , 2003Nightingale et al, 2002). The sunspot rotation is often accompanied by flares (Gopasyuk, 1965;Gopasyuk and Lazareva, 1986;Brown et al, 2003;Yan and Qu, 2007;Yan et al, 2008). Observations indicate that twisted loops exist in almost all the flare sites.…”

The rotation of sunspots in the solar active region NOAA 10930

“…The rotation velocity of the sunspots determined from the white light data is 5-6 times less than the azimuthal velocity calculated from the velocity field (Gopasyuk, 1981(Gopasyuk, , 1982Gopasyuk and Kosovichev, 2011). The appearance of the flares strongly correlates with the rotation of the sunspots (Gopasyuk, 1965;Gopasyuk and Lazareva, 1986;Brown et al, 2003;Yan and Qu, 2007;Yan et al, 2008).…”