Affiliation
Queen's University Belfast
Main category
Natural Sciences (Astrophysics and Astrononmy)
Abstract
Previous research has documented the ubiquitous presence of non-linear shocks that are introduced by upwardly propagating magneto-acoustic waves in sunspot umbral atmospheres. In recent years, extensive analyses have been undertaken to examine the effect of these shocks on the surrounding magnetically-dominated plasma, with previous work identifying line-of-sight modulations of the magnetic field strengths and temperature enhancements on the order of several hundred degrees Kelvin. We employ simultaneous slit-based spectro-polarimetry and spectral imaging observations of the chromospheric He I 10830Å and Ca II 8542Å lines to examine full vector fluctuations in the umbral magnetic field caused by the steepening of magneto-acoustic waves into umbral flashes. Following the application of the HAZEL inversion routine, we find evidence to support the scenario that umbral shock events cause expansion of the embedded magnetic field lines due to the increased adiabatic pressure, hence providing increased transversal magnetic field fluctuations up to ~200 Gauss. Through comparisons with non-linear force-free field extrapolations, we demonstrate how the development of umbral flashes can deflect the quiescent magnetic field geometry by up to 8 degrees in both inclination and azimuthal directions.
Further reading
http://adsabs.harvard.edu/abs/2018ApJ...860...28H
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