The Temperature Drift And Dynamical Evolution Of The Coronal Structure During Its Eruption

Solar flares and CMEs are energetic events which occur on the Sun,as the main source that disturb the space weather,deeply affect human life and techonology on earth.The two phenomena do sometimes occur at the same time.1.Thermodynamic Spectrum of Solar FlaresThe Solar Dynamics Observatory(SDO)/EUV Variability Experiment(EVE)pro-vides rich information on the thermodynamic processes of solar activities,particularly on solar flares.Here,we develop a method to construct thermodynamic spectrum(TDS)charts based on the EVE spectral lines.This tool could potentially be useful for extreme ultraviolet(EUV)astronomy to learn about the eruptive activities on distant astronomi-cal objects.Through several cases,we illustrate what we can learn from the TDS charts.Furthermore,we apply the TDS method to 74 flares equal to or greater than the M5.0 class,and reach the following statistical results.First,EUV peaks are always behind the soft X-ray(SXR)peaks and stronger flares tend to have faster cooling rates.There is a power-law correlation between the peak delay times and the cooling rates,suggesting a coherent cooling process of flares from SXR to EUV emissions.Second,there are two distinct temperature drift patterns,called Type ? and Type ?.For Type ? flares,the enhanced emission drifts from high to low temperature like a quadrilateral,whereas for Type ? flares the drift pattern looks like a triangle.Statistical analysis suggests that Type ? flares are more impulsive than Type ? flares.Third,for late-phase flares,the peak intensity ratio of the late phase to the main phase is roughly correlated with the flare class,and the flares with a strong late phase are all confined.We believe that the re-deposition of the energy carried by a flux rope,which unsuccessfully erupts out,into thermal emissions is responsible for the strong late phase found in a confined flare.Furthermore,we show the signatures of the flare thermodynamic process in the chro-mosphere and transition region in the TDS charts.These results provide new clues to advance our understanding of the thermodynamic processes of solar flares and associ-ated solar eruptions,e.g.,coronal mass ejections.2.Toward Understanding the Evolution of the Flux Rope in an Extremely-Long-Duration Eruptive FlareIn this work,we analyze the initial eruptive process of an extremely-long-duration flare occurred on June 21,2011.The flare,peaked at C7.7 level,had a two-hour-long rise time in soft X-rays emission;this rise time is much longer than the typical rise time of a normal solar flares which is only about ten minutes.Combining the facts that the flare occurred near the disk center as seen by Solar Dynamic Observatory(SDO),but near the limb as seen by two Solar Terrestrial Relations Observatory(STEREO)spacecraft,we are able to track the evolution of the eruption in 3-D which was in a rare slow-motion manner.The time sequence of the hot channel in the Atmospheric Imaging Assembly(AIA)94 A and 131 A passbands,clearly shows the process of how the sigmoid structure prior to the eruption was transformed into a near-potential post-eruption loop arcade.The observed sigmoid is likely to be the structure of a twisted magnetic flux rope(MFR),which reached a height of about 60 Mm at the onset of the eruption.The early onset of the pre-flare phase is likely triggered by the loss of the magnetostatic equilibrium of a pre-existing magnetic flux rope,which leads to the slow rising of the flux rope,the subsequent magnetic reconnection and/or flux rope instability cause the onset of the impulsive phase.