New HMI 96-minute vector magnetograms are now available. Deep averaging reduces noise and enhances long-lived magnetic structures.
A large sample statistical study of normalized Lorentz force and torques in emerging magnetic field shows that the photospheric magnetic field has a rather small Lorentz forces and torques, close to a force-free state.
Apparent 3-min waves observed inside sunspot umbrae are modeled as excited about 1000 to 2000 km beneath sunspots’ surface.
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.
The Sun’s poloidal and toroidal magnetic field components derived from synoptic magnetograms are assimilated into a mean-field dynamo model, and activity level for Cycle 25 is predicted based on this approach.
Electric current neutralization, which measures the ratio of direct current and return current inside active regions (ARs), is studied for a total of 30 AR samples. It is found that flare-productive ARs are more likely to exhibit non-neutralized currents than those flare-quiet ARs.
Newly developed time-distance helioseismic imaging method, which includes more multiskip acoustic waves, is proved to be more reliable in mapping the Sun’s far-side active regions.
This study explores the magnetic triggers of recurrent active region jets. Both widely debated triggers, namely, flux cancellation and flux emergence, are associated alternatively to the apparently homologous jets.
Of three consecutive flares that occurred in a same active region within 4 hours, why were two non-eruptive and one eruptive? Non-linear force-free modeling suggest that breakout reconnection during the first two flares weakened the overlying field, allowing the flux rope to erupt in the third.
In an MHD simulation of flux emergence, a δ-sunspot is formed spontaneously by a collision of areas with opposite polarities. Driven by convective flows and counter-streaming flows, sheared polarity inversion lines form and flux ropes are created above.