High abnormal rotation rates of sunspots and flare productivity

Suryanarayana, G.S.

doi:10.1016/j.newast.2009.09.004

Cited by 6 publications

(4 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…With the increase of observational capabilities both in sensitivity and resolution, sunspot rotation had drawn a considerable attention in an attempt to explain its characteristics in association with the transient activity. A majority of the studies based on observations examined the relationship between the sunspot rotation and coronal consequences (Brown et al 2003;Tian & Alexander 2006;Tian et al 2008), flare productivity (Yan et al 2008;Zhang et al 2008;Suryanarayana 2010), the association of flares with abnormal rotation rates (Hiremath & Suryanarayana 2003;Jiang et al 2012b), nonpotential parameters (Zhang et al 2007;Kazachenko et al 2009;Vemareddy et al 2012a), helicity injection (Vemareddy et al 2012b) etc.…”

Section: Introductionmentioning

confidence: 99%

Sunspot Rotation as a Driver of Major Solar Eruptions in the Noaa Active Region 12158

Vemareddy

Cheng

Ravindra

2016

ApJ

View full text Add to dashboard Cite

We studied the developing conditions of sigmoid structure under the influence of magnetic non-potential characteristics of a rotating sunspot in the active region (AR) 12158. Vector magnetic field measurements from Helioseismic Magnetic Imager and coronal EUV observations from Atmospheric Imaging Assembly reveal that the erupting inverse-S sigmoid had roots in the location of the rotating sunspot. Sunspot rotates at a rate of 0-5deg/h with increasing trend in the first half followed by a decrease. Time evolution of many nonpotential parameters had a well correspondence with the sunspot rotation. The evolution of the AR magnetic structure is approximated by a time series of force free equilibria. The NLFFF magnetic structure around the sunspot manifests the observed sigmoid structure. Field lines from the sunspot periphery constitute the body of the sigmoid and those from interior overly the sigmoid similar to a fluxrope structure. While the sunspot is being rotating, two major CME eruptions occurred in the AR. During the first (second) event, the coronal current concentrations enhanced (degraded) consistent with the photospheric net vertical current, however the magnetic energy is released during both the cases. The analysis results suggest that the magnetic connections of the sigmoid are driven by slow motion of sunspot rotation, which transforms to a highly twisted flux rope structure in a dynamical scenario. An exceeding critical twist in the flux rope probably leads to the loss of equilibrium and thus triggering the onset of two eruptions.

show abstract

Section: Introductionmentioning

confidence: 99%

Sunspot Rotation as a Driver of Major Solar Eruptions in the Noaa Active Region 12158

Vemareddy

Cheng

Ravindra

2016

ApJ

View full text Add to dashboard Cite

show abstract

“…This implies that the change in the areas of the sunspots is a rather gradual process along with the passage of the foot points through the width of rotational gradient beneath the surface. However, the occurrence of abnormal rotation rates of sunspots is a result that could be due to the flux tubes experiencing instability just below the surface where rotational gradient exists around the region of 0.935R s (Hiremath & Suryanarayana 2003;Suryanarayana 2010). This explains the result, presented in Fig.…”

Section: Discussionmentioning

confidence: 92%

“…A similar result was published in a study using substantial sunspot and flare data from Kodaikanal Observatory, which examined the association of the minimum separation between the bipolar sunspots and flare occurrences . The fact that high numerical flare productivity was observed in association with high abnormal rotation rates (ARR) of sunspots, leading to the inference that the instability experienced by the foot points of flux tubes below the photosphere (Hiremath & Suryanarayana 2003;Hiremath 2006) led to high flare productivity as well (Suryanarayana 2010). In this context, we note that the majority of spots that have leading and following parts are bipolar (Zirin 1988).…”

Section: Introductionmentioning

confidence: 80%

Abnormal rotation rates of sunspots and durations of associated flares

Suryanarayana

Hiremath

Bagare

et al. 2015

A&A

View full text Add to dashboard Cite

Context. Short-duration and long-duration flares are important in terms of their association with coronal heating and coronal mass ejections, respectively. Sunspot motions in the photosphere have been known to be associated with flare occurrences. Aims. We study the association between the abnormal rotation rates (longitudinal displacement in a given latitude in contrast with the rotation of spots around their umbral centre) of sunspots and flare duration. Methods. We compute the rotation rates of sunspots for different days during their evolution. We consider rotation rates that are in excess of one standard deviation as abnormal rotation rates. Also, the duration of time between the initial and final stages of the flares are computed. Results. Using Kodaikanal Observatory white light picture and GOES soft X-ray flare data, we find that a good association with a high significance exists between abnormal rotation rates of sunspots and flare durations. In contrast, we find that duration of flare is independent of sunspot area. Conclusions. The present study suggests that sub-surface dynamics plays a dominant role in determining the duration and rate of dissipation of energy during flares.

show abstract

“…The rotational motion of a sunspot can play an important role in twisting, energizing, and destabilizing the coronal magnetic field system (Fan (2009);Török et al (2013)). It has been widely reported that the continual rotational motions of sunspots were followed by flare activities (Brown et al 2003;Romano et al 2005;Régnier & Canfield 2006;Zhang et al 2007;Yan & Qu 2007;Li & Zhang 2009;Min & Chae 2009;Kazachenko et al 2009;Suryanarayana 2010;Jiang et al 2012;Zhu et al 2012;Kumar et al 2013;Ruan et al 2014;Bi et al 2015;Suryanarayana et al 2015;Li & Liu 2015;Wang et al 2016;Vemareddy et al 2016;Yan et al 2018).…”

Section: Introductionmentioning

confidence: 99%

A Survey of Changes in Magnetic Helicity Flux on the Photosphere During Relatively Low-class Flares

Liu

et al. 2018

ApJ

View full text Add to dashboard Cite

Using the 135-second cadence of the photospheric vector data provided by the Helioseismic and Magnetic Imager telescope on board the Solar Dynamic Observatory, we examined the time-evolution of magnetic helicity fluxes across the photosphere during 16 flares with the energy class lower than M5.0. During the flare in 4 out of 16 events, we found impulsive changes in the helicity fluxes. This indicates that even the flare with less energy could be associated with anomalistic transportation of the magnetic helicity across the photosphere. Accompanying the impulsive helicity fluxes, the poynting fluxes across the photosphere evolved from positive to negative. As such, the transportations of magnetic energy across the photosphere were toward solar interior during these flares. In each of the 4 events, the impulsive change in the helicity flux was always mainly contributed by abrupt change in horizontal velocity field on a sunspot located near the flaring polarity inversion line. The velocity field on each sunspot shows either an obvious vortex patten or an shearing patten relative to the another magnetic polarity, which tended to relax the magnetic twist or shear in the corona. During these flares, abrupt change in the Lorentz force acting on these sunspots were found. The rotational motions and shearing motions of these sunspots always had the same directions with the resultant Lorentz forces. These results support the view that the impulsive helicity transportation during the flare could be driven by the change in the Lorentz force applied on the photosphere.

show abstract

High abnormal rotation rates of sunspots and flare productivity

Cited by 6 publications

References 14 publications

Sunspot Rotation as a Driver of Major Solar Eruptions in the Noaa Active Region 12158

Sunspot Rotation as a Driver of Major Solar Eruptions in the Noaa Active Region 12158

Abnormal rotation rates of sunspots and durations of associated flares

A Survey of Changes in Magnetic Helicity Flux on the Photosphere During Relatively Low-class Flares

Contact Info

Product

Resources

About