We observed magnetoacoustic waves propagating along the magnetic field lines of a sunspot. Based on the wave periods and atmospheric characteristics, we reconstructed the magnetic field topology of the sunspot.
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 newly discovered, fast-moving wave propagates outward along sunspots’ radial direction and may provide new diagnostics of the sunspot subsurface structure.
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.
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.
Taking advantage of 11 different databases, we use statistical analysis to probe the nature of photospheric magnetic structures. We find evidence of two separate mechanisms at play, and propose that they are directly connected to the global and small-scale components of the solar dynamo.
Flow system in an average supergranule is compared to the moat flow around axisymmetric sunspots. Both phenomena are very similar, only the outflow in the moat is distorted due to the proper motion of the sunspot with respect to the local frame of rest and moat is a purely downflow region.
The statistical analysis of flow fields in and around sunspots indicates a distinct nature of the moat and Evershed flows.
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 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.