Statistical analysis of sunspot groups and flares for solar maximum and minimum

Abstract

Based on the NOAA/SWPC data, by choosing two separative periods with successive 12 months, that is, 2005 July–2006 June(during the solar minimum) and 2011 July–2012 June(during the solar maximum), we analyze the activity of flares and compare the statistical results between the two periods for studying their evolution with time, sunspot distribution, sunspot lifetime and magnetic field types. The main conclusions are:(1) The time variation of sunspot groups number is random for both the solar minimum and maximum periods. The sunspot number during the solar maximum is about 1.5 times larger than during the solar minimum. The flare number shows good correlation with the sunspot group number. During solar maximum there may be very few flares for some months, while during solar minimum there can be plenty of flares for some months, indicating the importance of keeping monitoring for solar activities even during the solar minimum period.(2) The δ-sunspot groups have the highest flare productivity(the ratio of flare amount to sunspot group number) for both solar minimum and maximum, while the β-sunspot groups have produced the most flares. The flare productivity of sunspot groups has close relation with magnetic field type, and it has no obvious relation with the state of solar cycle.(3) There is serious asymmetry in the distribution for flares, especially for X-class flares. The increase of the flares number from solar minimum to maximum is mainly caused by C- and M-class flares.(4) The number of sunspot groups has no obvious correlation with their lifetime, while the flare productivity shows well correlation with sunspot lifetime for all periods.