The magnetic twist of a flux rope is carefully calculated for an active region model. The flux rope is close to the threshold of helical kink instability and has powered a series of eruptions.
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.
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.
The magnetic field of active region NOAA 11092 shows a persistent counter-clockwise twist in the solar atmosphere from the photosphere to the corona. The subsurface flows associated with this region are twisted in the opposite direction.
Combining the outstanding capability of HMI/SDO and NST/BBSO, we studied two rarely observed three-ribbon flares. The flaring site is characterized with an intriguing “fish-bone”-like morphology. These results are discussed in favor of reconnection along the coronal null-line.
Analysis of HMI vector magnetic field data before and after a flare illustrate how the energy released can result in a collapse of loop structures, and how the effects can be observed on the solar surface.
We present observations from SDO/HMI of a magnetic transient observed in NOAA 11429 during the M7.9 flare on 13 March 2012. The observed transient showed an impulsive rotation of the field vector in response to the white-light flare.