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.
Subsurface meridional flow speed shows an anti-correlation with the magnetic flux being transported poleward above the latitude of 35°. In the lower latitude, the residual meridional flow, after a long-time mean profile is subtracted, shows converging flow toward the activity belts.
The Lorentz force acting on the solar atmosphere is useful for diagnosing the eruption dynamics. It is now available as a routine data product.
The statistical analysis of flow fields in and around sunspots indicates a distinct nature of the moat and Evershed flows.
Bertello and collaborators at NSO have made a first attempt to estimate some of the uncertainties in magnetic synoptic maps and evaluated their impact on coronal and heliospheric models. They found that accounting for the statistical uncertainties arising from the distribution of image pixels contributing to each bin in the synoptic map may produce a noticeable change in the results obtained from these models.
Our results show that raising the source surface height 15-30% during solar minimum (depending on the model used) better reproduces the observed IMF open flux from OMNI. We used two different PFSS models and the MDI/HMI magnetograms as input.
We have seen that the quiescent photospheric magnetic field is composed of multiple connective scales. The observed scales range from a few megameters to those that are 100 –250 Mm in scale. We expect that the latter of these scales belongs to a spatially large, deep and hence slowly overturning convective flow — one that possibly reaches to the bottom of convection zone.
I investigate the possible long term decrease in umbral magnetic field strengths from 1998-2006. Whereas a decrease of 800 Gauss in umbral magnetic fields has been reported between 1998 and 2012, the HMI and MDI data indicate a decrease of only around 300 Gauss. The continuing availability of the excellent HMI data set will allow us to continue to refine this study as solar cycle 24 evolves.
We examine the polarization of light emitted by a loop prominence system, near the Fe I line (6173 Å). It has a linearly polarized component, at times up to the level expected from pure Thomson scattering.
Reports of white-light ejecta above the limb of the Sun and imaged without the aid of a true coronagraph are exceedingly rare. Here we report the successful use of HMI to observe flare effects in the corona by the use of differencing as a substitute for an actual occulter.