The systematic Center-to-Limb effect in time-distance helioseismic measurements is found to be significantly frequency dependent. The dependence further varies with disk-centric distance but not with travel distance.
Vector magnetic fields, obtained separately from the HMI and from the Stokes parameters of Hinode, are compared for a sunspot umbra, penumbra, and plages in a selected active region.
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.
The Sun’s surface poloidal and toroidal magnetic field were constructed for the last 4 solar cycles using observations from multiple instruments, and were then reproduced using the updated Babcock-Leighton model.
Super-synoptic map is constructed using SDO/HMI’s synoptic magnetic maps of each Carrington rotation, covering the period of May 2010 to December 2017. Polarity reversals can be clearly seen in the map.
The dipole, quadrupole, and octupole components of the Sun’s magnetic field are calculated and visualized, covering the last 22 years of the Sun’s activities.
The Sun’s meridional flow varies with the solar cycle, and this is possibly caused by the back-reaction of the dynamo-generated magnetic field on the meridional flow due to the Lorentz force.
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.
The dipole moment observed by the WSO during the pre-minimum years of the last 4 solar cycles are used to establish a relation with the sunspot numbers of the following maximum years. The relation is then used to calculate the dipole moment for all the past cycles.
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.