Interactions between nested sunspots II. A confined X1 flare in a delta-type sunspot

摘要: We study the flaring activity in a nest of sunspots which two bipolar regions emerge inside third one. These belong to large complex (McMath 15314) formed by five bipoles on its May 1978 rotation. The usual spreading action during growth leads formation �-configuration: preceding and follow- ing spots interior overlap (p-f collision) into single penumbra. While �-configurations created this way normally favor strong activity, only very small flares oc- cur 5 days. Only when following umbra �-spot breaksintopieces,accompaniedbyrapidphotosphericmotions, do intenseflares occur. largest best observed one sequence,aclass1B/X1flareon28May1978,isremarkablefor absence ejecta for concentration emission three widely spaced sites, pattern holds general over days lesser flares. take as evidence that flare is confined low corona. first compute coronal magnetic field using subphotospheric sources model data derive location separa- trices. In case topology defined link between these discrete sources. relevant generaliza- tion separatrices any kind configuration are 'quasi-separatrix layers' (QSLs). calculate them previous model, but also obtained with more clas- sicalextrapolationtechniquebasedonthefastFouriertransform method. show, both approaches, plage bright- enings quiescent phase region kernels located at intersection QSLs photosphere. Moreover, they magnetically linked. Bright dark 'post'-flare loops form maximum gradual phases 1B/X1 highlight loca- QSLs. This confirms studies importance Send offprint requests to: V. Gaizauskas ? C.H.M. M.G.R. Members Carrera del Investigador CientCONICET and, study, we further constrain underlying physical mechanism. draw some conclusions about role reconnection solar corona; depending photospheric conditions identify, can lead steady heating or flaring.