CHEN Guorong and Prof. YAN Xiaoli from Yunnan Observatories of Chinese Academy of Sciences, investigated a series of confined solar flares occurring in active region NOAA 11861. The results were recently published in The Astrophysical Journal.

Solar flare is one of the violent eruptive activities, which may cause the disaster space weather. Studies on the trigger mechanisms of solar flares are quite important in predicting the occurrence of solar flares.

Solar flares with a similar topology and an analogous triggering mechanism are named as homologous solar flares. By using the Hα data from the New Vacuum Solar Telescope (NVST) at the Fuxian Solar Observatory and multi-wavelength images and magnetograms obtained by the Solar Dynamics Observatory (SDO), the researchers studied the detailed process of three homologous confined flares in active region NOAA 11861.

Through analyzing the evolution of magnetic field and flow field, they found an obvious magnetic emergence and a strong shearing motion between two opposite polarities near the following sunspot. Before the occurrence of the solar flares, magnetic cancellation already appeared. The interaction between the emerging magnetic fields and pre-existing magnetic fields is believed as the starting of the solar flares. Meanwhile, the reconnection between different loops was observed in Hα images at the beginning of each flare.

In previous studies, the source of energy injection is thought to be the area with strong up-flows in the surrounding of leading sunspot and emerging magnetic region. However, whether the energy across the photosphere is enough for a specific flare is not determined.

By calculating the shearing and the emergence energy in the photosphere, they found that the integral of energy injected from the photosphere, for a few hours, could provide enough energy for the solar flares.

Contact:

YAN Xiaoli, Yunnan Observatories , CAS
yanxl@ynao.ac.cn