Omnipresent magneto-acoustic waves, originating from within the underlying sunspot and propagating radially outwards, allow the spatial variation of the local coronal magnetic field to be mapped with high precision.
The effect of the spatial resolution of the boundary data on nonlinear force-free extrapolations is systematically explored for a solar case.
Multiple-wavelength high-resolution observations reveal running penumbral waves in the middle photosphere, with an apparent horizontal speed of up to 51 km/s.
A statistical study using HMI vector magnetograms predicts the fastest CME that an active region can produce based on its magnetic parameters.
Surface flux transport model suggests that the weak Cycle 24 is mainly caused by a number of bigger bipolar regions emerging at low latitudes with a “wrong” north-south orientation.
Solar inter-network magnetic field, the weakest component of the solar magnetism, seems to be invariant at ~10 G from the minimum to the maximum phase of Cycle 24. This suggests a possible origin of small-scale, local dynamo.
Numerical simulation of sunspots indicate that different subsurface structures are possible. They may be deep coherent flux tubes or twisted spaghetti or shallow structures. It may well be that all the models proposed for sunspot structures are correct for some spot somewhere.
AR 12192 produced six X-class flares, but none was associated with a CME. HMI observations reveal the mild nature of the giant. It has weak relative non-potentiality and strong overlying field; the confined X3 flare leaves little imprint on the photosphere.
Are all sunspots created equal or are some sunspots formed by a different mechanism than others? High quality observations from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) suggest bimodal distribution in properties of sunspots.
We present potential filed and nonlinear force-free magnetic field (NLFFF) extrapolations of full-disk magnetogram observed by SDO/HMI instrument. The study shows that NLFFF model agrees significantly better with coronal magnetic loops as observed in SDO/AIA images.