Abstract


  RUNNING PENUMBRAL WAVE FILTERING THROUGH INCLINED SUNSPOT MAGNETIC FIELDS

  D. Jess, Queens University Belfast, d.jess@qub.ac.uk

High spatial and temporal resolution images obtained using both ground- and space-based instrumentation are used to investigate the role magnetic fields
play in the propagation characteristics of running penumbral waves in the solar chromosphere. Analysis of a near-circular sunspot, close to the centre of the
solar disk, reveals a smooth rise in oscillatory period as a function of distance from the umbral barycenter. However, in one directional quadrant, corresponding
to the north direction, a pronounced kink in the period–distance diagram is found. Utilising a combination of the inversion of magnetic Stokes vectors and
force-free field extrapolations, we attribute this behaviour to the cut-off frequency imposed by the magnetic field geometry in this location. A rapid, localised
inclination of the magnetic field lines in the north direction results in a faster increase in the dominant periodicity due to an accelerated reduction in the cut-
off frequency. For the first time, we reveal how the spatial distribution of dominant wave periods, obtained with one of the highest resolution solar instruments
currently available, directly reflects the magnetic geometry of the underlying sunspot, thus opening up a wealth of possibilities in future magnetohydrodynamic
seismology studies. In addition, the intrinsic relationships we find between the underlying magnetic field geometries connecting the photosphere to the
chromosphere, and the characteristics of running penumbral waves observed in the upper chromosphere, directly supports the interpretation that running
penumbral wave phenomena are the chromospheric signature of upwardly propagating magneto-acoustic waves generated in the photosphere. With the
upcoming National Large Solar Telescope, I will also discuss how new-age large-format sCMOS camera systems will allow for unprecedented views of wave
phenomena in the lower solar atmosphere when combined with the 2m Indian facility.