Extreme-ultraviolet Late Phase in Homologous Solar Flares from a Complex Active Region

Recent observations in extreme-ultraviolet (EUV) wavelengths reveal a new late phase some solar flares, which is seen as second peak warm coronal emissions ($\sim3$ MK) several tens of minutes to few hours after the soft X-ray (SXR) peak. The origin EUV (ELP) explained by either long-lasting cooling process long ELP loops, or delayed energy ejection into loops well main flare heating. Using with \emph{Solar Dynamics Observatory} (\emph{SDO}), we investigate production six homologous flares (F1--F6) originating from complex active region (AR) NOAA 11283, an emphasis on emission characteristics flares. It found that mechanism changes additional heating F1 F3--F6, both mechanisms playing role F2. transition evidenced abrupt decrease time lag peak, and majority validated positive correlation between ribbon fluence intensity. We attribute change enhancement envelope magnetic field above AR, facilitates more prompt energetic loops. In addition, last only confined F6 exhibits extremely large ELP. different pattern revealed this may reflect partitioning inside due reconnection process.