Relationship between magnetic field evolution and flaring sites in AR 6659 in June 1991

Schmieder, B.; Hagyard, M. J.; Ai, Guoxiang; Zhang, Hongqi; Kalman, B.; Györi, L.; Rompolt, B.; Démoulin, P.; Machado, M. E.

doi:10.1007/bf00712886

Cited by 64 publications

(37 citation statements)

References 18 publications

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“…These strong electrical currents do not persist for more than about a day (e.g., Pevtsov et al 1994;Schrijver et al 2005) unless sustained by continued flux emergence. It is therefore no surprise that the emergence of compact field has also been found to be positively correlated with some flaring (e.g., Schmieder et al 1994;Wang et al 1994;Choudhary et al 1998;Li et al 2000).…”

Section: Introductionmentioning

confidence: 99%

A Characteristic Magnetic Field Pattern Associated with All Major Solar Flares and Its Use in Flare Forecasting

Schrijver

2007

ApJ

322

348

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Solar flares result from some electromagnetic instability that occurs within regions of relatively strong magnetic field in the Sun's atmosphere. The processes that enable and trigger these flares remain topics of intense study and debate. I analyze observations of 289 X-and M-class flares and over 2500 active region magnetograms to discover (1) that large flares, without exception, are associated with pronounced high-gradient polarity-separation lines, while (2) the free energy that emerges with these fibrils is converted into flare energy in a broad spectrum of flare magnitudes that may well be selected at random from a power-law distribution up to a maximum value. This maximum is proportional to the total unsigned flux R within ∼15 Mm of strong-field, high-gradient polarityseparation lines, which are a characteristic appearance of magnetic fibrils carrying electrical currents as they emerge through the photosphere. Measurement of R is readily automated, and R can therefore be used effectively for flare forecasting. The probability for major flares to occur within 24 hr of the measurement of R approaches unity for active regions with the highest values of R around Mx. For regions with Mx, no

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Section: Introductionmentioning

confidence: 99%

A Characteristic Magnetic Field Pattern Associated with All Major Solar Flares and Its Use in Flare Forecasting

Schrijver

2007

ApJ

322

348

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“…By considering the H-α filament as a proxy for the magnetic neutral line, Sivaraman et al (1992) quantitatively estimated change in the shear that corresponds with the occurrence of the flare. Schmieder et al (1994) showed that in order to have the flare occurrences, the following two conditions are necessary: (i) the break up motions of different polarity regions maintained a high shear level for the continuous build up of the magnetic flux and, (ii) the rapid motions and the changes in the magnetic sources.…”

Section: Introductionmentioning

confidence: 99%

The flares associated with the abnormal rotation rates of the bipolar sunspots: Reconnection probably below the surface

Hiremath

Suryanarayana

2003

A&A

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Abstract.We use the observations of Kodaikanal observatory white light pictures to study the association between the rotation rates of the bipolar sunspots and triggering of the flares. For the years 1969−1974, we compute daily rotation rates of the leading and the following spots of the bipolar sunspot groups during their life span. We find that either leading or following or both of the bipolar spot groups which have abnormal rotation rates during the course of their evolution are strongly associated with the occurrence of flares in the later stage of their life span. Other important findings are: (i) the abnormal rotation rates and the flares occur during the 50−80% of their life span of the spot group and, (ii) abnormal rotation rate of about 2• /day is required for triggering the flares. The strong relation between the occurrence of abnormal rotation rates of the sunspot groups and the occurrence of the flares enabled us to estimate the probable region of depth of reconnection below the solar surface.

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“…A key point seems to be magnetic complexity, invoking magnetic reconnection between colliding flux tubes as a possible triggering process (e.g., Sturrock et al 1984). Indeed, the non-potential magnetic field topology is thought to be responsible for the sudden release of the free magnetic energy taking place around the sheared polarity inversion line (PIL; Hagyard et al 1984;Patty & Hagyard 1986;Machado et al 1988;Mandrini et al 1993;Schmieder et al 1994;Liu & Zhang 2001;Leka & Barnes 2003;Tian et al 2005), through the interaction of the opposite-oriented flux systems or due to the compact electrical currents generated in the presence of high-gradient magnetic fields (Schrijver 2007). The evolution of the magnetic shear in complex emerging flux regions is studied in several numerical simulations (e.g., Linton et al 1998Linton et al , 1999Fan & Gibson 2004;Zaqarashvili et al 2010;Fang et al 2012aFang et al , 2012bToriumi et al 2014).…”

Section: Introductionmentioning

confidence: 99%

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

Guglielmino¹,

Zuccarello²,

Romano

et al. 2016

ApJ

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We present an analysis of multi-instrument space-and ground-based observations relevant to a C4.1 solar flare that occurred in the active region (AR) NOAA 11267 on 2011 August 6. Solar Dynamics Observatoryobservations indicate that at the flare's beginning, it was localized in the preceding sunspot of the AR, which exhibits a δ configuration. Along the polarity inversion line between its opposite polarities we find a large shear angle of about 80°. The helicity accumulation shows that the AR does not obey the general hemispheric helicity rule. At the flare peak, unique observations taken with the X-Ray Telescope aboard Hinode reveal that the bulk of the X-ray emission takes place in the δ-spot region, where the plasma heats up to 1.9 10 7 · » K. During the gradual phase, we observe the development of a Y-shaped structure in the corona and in the high chromosphere. An extruding structure forms, being directed from the emitting region above the δ spot toward the following sunspot. This structure cools down in a few tens of minutes while moving eastward along a direction opposite to the flare ribbon expansion. Finally, remote brightenings are found at the easternmost footpoint of this structure, appearing as a third flare ribbon in the chromosphere. After some minutes, RHESSI measurements show that the X-ray emission is localized in the region close to the crossing point of the coronal Y-shaped structure. Simultaneously, highresolution (0 15) observations performed at the Swedish 1 m Solar Telescope indicate a decreasing trend of the Ca II H intensity in the flare ribbons with some transient enhancements. All these findings suggest that this event is a manifestation of magnetic reconnection, likely induced by an asymmetric magnetic configuration in a highly sheared region.

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Relationship between magnetic field evolution and flaring sites in AR 6659 in June 1991

Cited by 64 publications

References 18 publications

A Characteristic Magnetic Field Pattern Associated with All Major Solar Flares and Its Use in Flare Forecasting

A Characteristic Magnetic Field Pattern Associated with All Major Solar Flares and Its Use in Flare Forecasting

The flares associated with the abnormal rotation rates of the bipolar sunspots: Reconnection probably below the surface

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

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