Solar flares are thought to be one of the violent energetic events involved in the sudden release of magnetic energy stored in the active region(AR). The flares are accompanied with a series of high energy phenomenon, such as,𝛾 ray and Xray. Some flares are involved with ejecting a large amount of magnetic structures and materials into interplanetary space, which is known as CMEs. The flares can strongly affect the space environment of earth. Thus, the accuracy in the predicting of the flares are quite significant. Studies on the trigger mechanisms of solar flares are quite important in predicting the occurrence of flares. By using H𝛼 data from the New Vacuum Solar Telescope(NVST) at the Fuxian Solar Observatory together with multi-wavelength images and magnetograms obtained by the Solar Dynamics Observatory, we study the detailed process of three homogenous confined flares in active region NOAA 11861 on 2013 October 12. As shown in the multi-wavelength images, all of the three flares occurred at the same location, with similar morphologies and comparable classes. These flares can be implied as homogenous flares. Through analyzing the evolution of magnetic field and flow field, we found an emergence of magnetic flux and a strong shearing motion between two opposite polarities near the following sunspot. The magnetic flux and the average transverse field strength exhibited a decrease before a few moment of each eruption and reached the lowest point at the onset of each eruption. We deduce that the flux cancellation may have been going on a few before the eruptions. Meanwhile, the reconnection between different loops was observed in H𝛼 images during the occurrence of each flare. These result suggest that the shearing motion and flux emergence drive the magnetic reconnection between the different loops to destabilize the topology of magnetic structure and finally triggered these eruptions. The free energy to power the flares can be accumulated by the emerging and shearing motion of photosphere. By calculating the shearing and the emergence energy in the photosphere, we found that the integral of energy injected from the photosphere, for a few hours, could provide enough energy for the flares. In summary, the emerging magnetic flux and the shearing motion in the photosphere can inject the energy to the sheared magnetic loops and the energy was finally released via magnetic reconnection to power the solar flares.
修改评论