An unsupervised machine-learning algorithm is used on selected features derived from the polarity inversion lines (PIL) mask and difference PIL mask. It is found these features are effective in predicting flaring occurrences.
A strong limb flare observed simultaneously by the SDO/AIA and SDO/HMI, which is very rare, allows the authors to study the emission mechanism for white-light flare loops, as well as estimate the electron densities along the flare loop.
A total of 90 circular-ribbon flares are identified in 8 years of SDO observations, and 33 of them are found associated with white-light enhancements, a rate higher than non-circular-ribbon flares. It is thus suggested that the fan-spine magnetic field topology and the total amount of energy release plays roles in causing white-light flares.
AR12192, the largest active region in Solar Cycle 24, produced 6 X-class flares, but none of them were associated with a CME. However, a much weaker flare, of M4.0-class, was associated with a CME. Magnetic field and morphological changes are analyzed during these flares to understand why this is the case.
44 strong flares are analyzed, and a few factors are identified to determine whether a flare will be eruptive or confined.
Magnetic field changes associated with solar flares, observed by the SDO/HMI, are surveyed, and permanent changes of magnetic field are found in the majority of flare events. Properties of the magnetic field changes are further investigated.
Two homologous circular-ribbon flares associated with two filament eruptions were observed and analyzed. The emergence of magnetic flux ropes helped to inject free energy into the region and drive the magnetic reconnection above it.
Statistical studies find that white-light flares from the Sun and from solar-type stars have similar energy-duration relations, but the stellar flares have shorter duration. Cooling effect and stronger magnetic field in the stellar corona are proposed to explain this difference.
What makes the limb flares detectable in visible lights, hydrogen recombination or Thomson scattering?