| dc.description.abstract | In this thesis, I analyze the light curves of 77 G type stars observed by Kepler Mission based on flaring events and well-defined periodicity, and find 4944 confirmed superflares excluding the false events. By estimating the flares duration and flare energy with Stefan-Boltzmann law, I find the superflares have energy on average of 5×1034 - 1036 ergs and saturation with 2×1037 ergs. Furthermore, the long duration flares tend to have smaller flare amplitudes with several bumps in the decay phase, while short duration flares have higher amplitudes with smooth decay. Additionally, the power-law index γ values vary widely from 0.68±0.24 to 2.91±0.29, suggesting that the stars are at random phases, and have different chromospheric activities. If we only consider the stars with flare percentage larger than 10%, the γ values have range 1.2-2.18. Additionally, a trend is shown that the stars with shorter rotation periods tend to have larger power-law indices. Moreover, two indicators of the stellar activity show that most of the stars have 3-20 superflares a year; and that the stars generally have spot coverage 0.5 - 5% of surface. The lowest limit of spot size to produce superflares need to be larger than 0.5% of stellar surface, which is the size of the biggest sun spot in 1947. And most of superflares with 1034-1035 ergs have 8-25% spot coverage. Besides, the relation between stellar phase and flare timing shows that there are 7.3% of superflares occur at the dimmer part of light curve, and 9.5% at the brightest part of light curves. | en_US |