A Kinematic And Thermodynamic Study Of Confined Solar Eruptions

It is found that solar eruptions with different morphology and scales occur in the solar atmosphere all the time.The nature and physical mechanism of these eruptions are frontier topics in solar physics,and are important bases for accurate space weather forecast.In the past few decades,a physical model has been proposed for explaining eruptive flares,namely the standard flare model.However,whether the standard flare model can also be applied to confined flares and small-scale eruptions still needs to be detailedly studied.For this purpose,we firstly select 26 confined flares accompanying with the ascending hot structures and mainly focus on their early kinematic evolution.It is found that all the ascending structures experience an impulsive acceleration phase followed by a fast deceleration one.Moreover,the velocity evolution of the hot blobs is found to be roughly synchronized with the soft X-ray(SXR)light curve of the associated confined flares.However,we also notice an offset between the peak time of the velocity and that of the flare SXR flux,which could be due to that the constraint of the overlying field prevents the eruption,which thus weakens the reconnection.Next,we study 4confined flares with X-ray sources in the corona,and analyze their temperature and the properties of the corresponding X-ray sources.We find that the X-ray sources always appear at the top of the flare loops,and below or inside the erupting hot structures.In one of these cases,the eruption also causes an inverted Y-shape hot structure,which is highly similar to the eruptive flares.However,the X-ray spectra of these 4 flares show that their thermal energy is much greater than non-thermal energy,which indicates that the origin of the energy released is mainly thermal.Moreover,in the study of the minisigmoid in a corona hole,we find that the transition from the two J-shape structures into a sigmoidal structure is closely related to the flux cancellation in the source region.Through the reconstruction method,we study the topology of the magnetic field in the corona and the corresponding electric current and squashing factor,which prove the important role of the flux rope and the magnetic reconnection in this kind of small-scale events.It can be concluded from above results that the standard flare model involving erupting flux rope and the magnetic reconnection could also be applied to part of the confined flares and small-scale eruptions.