Flaring Rates and the Evolution of Sunspot Group McIntosh Classifications

Sunspot groups are the main source of solar flares, with the energy to power them being supplied by magnetic-field evolution (e.g. flux emergence or twisting/shearing). To date, few studies have investigated the statistical relation between sunspot-group evolution and flaring, with none considering evolution in the McIntosh classification scheme. Here we present a statistical analysis of sunspot groups from Solar Cycle 22, focusing on 24-hour changes in the three McIntosh classification components. Evolution-dependent ≥C1.0$\ge \mathrm{C}1.0$, ≥M1.0$\ge \mathrm{M}1.0$, and ≥X1.0$\ge \mathrm{X}1.0$ flaring rates are calculated, leading to the following results: i) flaring rates become increasingly higher for greater degrees of upward evolution through the McIntosh classes, with the opposite found for downward evolution; ii) the highest flaring rates are found for upward evolution from larger, more complex, classes (e.g. Zurich D- and E-classes evolving upward to F-class produce ≥C1.0$\ge \mathrm{C}1.0$ rates of 2.66±0.28$2.66\pm 0.28$ and 2.31±0.09$2.31 \pm 0.09$ flares per 24 hours, respectively); iii) increasingly complex classes give higher rates for all flare magnitudes, even when sunspot groups do not evolve over 24 hours. These results support the hypothesis that injection of magnetic energy by flux emergence (i.e. increasing in Zurich or compactness classes) leads to a higher frequency and magnitude of flaring.

[1]  D. S. Bloomfield,et al.  The Evolution of Sunspot Magnetic Fields Associated with a Solar Flare , 2011, 1105.1978.

[2]  D. Nandy,et al.  Spatial Relationship between Twist in Active Region Magnetic Fields and Solar Flares , 2005 .

[3]  Herschel B. Snodgrass,et al.  Rotation of Doppler Features in the Solar Photosphere , 1990 .

[4]  D. S. Bloomfield,et al.  Evidence for Partial Taylor Relaxation from Changes in Magnetic Geometry and Energy during a Solar Flare , 2012, 1212.5906.

[5]  Haimin Wang,et al.  Active-Region Monitoring and Flare Forecasting – I. Data Processing and First Results , 2002 .

[6]  C. Schrijver,et al.  The Nonpotentiality of Active-Region Coronae and the Dynamics of the Photospheric Magnetic Field , 2005 .

[7]  Yong-Jae Moon,et al.  Solar Flare Occurrence Rate and Probability in Terms of the Sunspot Classification Supplemented with Sunspot Area and Its Changes , 2012 .

[8]  D. S. Bloomfield,et al.  Performance of Major Flare Watches from the Max Millennium Program (2001 – 2010) , 2015, 1512.04518.

[9]  A. Cortie On the Types of Sun-Spot Disturbances , 1901 .

[10]  D. Rust,et al.  Quantitative Forecasting of Major Solar Flares , 2007 .

[11]  P. Bornmann,et al.  Flare rates and the McIntosh active-region classifications , 1994 .

[12]  H. Künzel,et al.  Die Flare-Häufigkeit in Fleckengruppen unterschiedlicher Klasse und magnetischer Struktur (Mitteilungen des Astrophysikalischen Observatoriums Potsdam Nr. 87) , 1959 .

[13]  Michael S. Wheatland,et al.  Rates of Flaring in Individual Active Regions , 2001 .

[14]  Guoxiang Ai,et al.  Relationship between magnetic field evolution and flaring sites in AR 6659 in June 1991 , 1994 .

[15]  Carolus J. Schrijver,et al.  A Characteristic Magnetic Field Pattern Associated with All Major Solar Flares and Its Use in Flare Forecasting , 2007 .

[16]  R. Giovanelli,et al.  The Relations Between Eruptions and Sunspots. , 1939 .

[17]  G. A. Gary,et al.  Magnetogram Measures of Total Nonpotentiality for Prediction of Solar Coronal Mass Ejections from Active Regions of Any Degree of Magnetic Complexity , 2008 .

[18]  George E. Hale,et al.  The Magnetic Polarity of Sun-Spots , 1919 .

[19]  P. McIntosh The classification of sunspot groups , 1990 .

[20]  Y. Moon,et al.  Propagation of Interplanetary Coronal Mass Ejections: The Drag-Based Model , 2013 .

[21]  M. Crown,et al.  Validation of the NOAA Space Weather Prediction Center's solar flare forecasting look‐up table and forecaster‐issued probabilities , 2012 .

[22]  D. S. Bloomfield,et al.  TOWARD RELIABLE BENCHMARKING OF SOLAR FLARE FORECASTING METHODS , 2012, 1202.5995.

[23]  B. R. Dennis,et al.  GLOBAL ENERGETICS OF THIRTY-EIGHT LARGE SOLAR ERUPTIVE EVENTS , 2012, 1209.2654.

[24]  Harold Zirin,et al.  The Dependence of Large Flare Occurrence on the Magnetic Structure of Sunspots , 2000 .