Energy Partition In Confined Circular-ribbon Flares

Solar flare is one of the main explosive activities on the Sun,which can release a large amount of energy in a short period of time.It can be divided into eruptive flares and confined flares depending on its association with or without coronal mass ejection.The physical process of the flare is quite complicated.During this period,various energies are converted and various forces affect each other.Therefore,it is extremely difficult to obtain physical models that perfectly explain the flare.By calculating the energy partition of the flare,certain parameter limits can be given to flare model,and it is of great significance for the verification of physical concepts such as magnetic reconnection and the study of space weather.There are many researches on the energy partition of eruptive flares,but there are few studies on the energy partition of con-fined flares.Therefore in this thesis we will do further calculations and explorations on the energy partition of confined flares.We have selected four confined circular-ribbon flares(CRFs)located near the center of the solar disk,two of which were M-class and two were C-class.These flares occurred on 10 May 2012,7 November 2013,29 December 2013 and 5 March 2014,respectively.Using the observations by SDO,GOES and RHESSI,we have calculated the various energy components of each flare,including radiated energy in 1-8 A,1-70 A,70-370 A,the total radiation loss of the thermal plasma,the peak thermal energy,the non-thermal energy of accelerating electrons,and the free magnetic energy.The calculation results show that the radiated energy in 1-70 A is much larger than that in 70-370 A,and non-thermal energy is more than the sum of peak thermal energy and radiation loss,which shows that non-thermal energy is sufficient to provide the heating requirements(the peak thermal energy and radiation loss).The calculation results also show that the free magnetic energy stored before the flare is larger than other energy components,and the values of basically all energy components are positively correlated with the flare class,which also reveals that the greater energy stored and released by the larger flares.By calculating the ratio of the non-thermal energy to the free magnetic energy Enth/Emag of the four CRFs,comparing with the previous study on the eruptive flares,it is found that the value(0.70-0.76)is greater.This may be used as a distinction between eruptive flares and confined flares.