Where does a sunspot’s penumbra start to form, on the same side or the opposite side of its opposite-polarity sunspot? When does Evershed flow start to appear, before or after the penumbral formation? These questions are answered through analyzing selected samples observed by the HMI.
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.
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.
Helioseismic far-side images are compared with the STEREO-AIA EUV observations, and a reliability of the helioseismic images is assessed.
What makes the limb flares detectable in visible lights, hydrogen recombination or Thomson scattering?
Through analyzing a suite of space- and ground-based observations, the authors report that above sunspots, helioseismic waves of different frequencies are able to channel up through the chromosphere and transition region into corona. General pictures of how the waves make into corona are also shown.
We have generated a dataset of emerging active regions (EARs) observed by SDO/HMI that is specifically suitable for helioseismic analysis. Using this dataset we show that, on average the bipoles have a symmetric the east-west velocity relative to differential rotation.
We observed magnetoacoustic waves propagating along the magnetic field lines of a sunspot. Based on the wave periods and atmospheric characteristics, we reconstructed the magnetic field topology of the sunspot.
By synthesizing the results of photospheric field change indicated by HMI observations and coronal field variation suggested by the NLFFF modeling, we study the flare-related 3D magnetic restructuring and find it consistent with the coronal implosion scenario in the low solar atmosphere.