Speaker
Christopher Nelson
(University of Sheffield & Queen's University Belfast)
Description
Modern high-resolution observations have highlighted the ubiquity of small-scale
structures in sunspot umbrae. Umbral micro-jets, extended bright features which were
originally identified within Ca II H filtergrams, are one interesting example of such
structuring. These bright elongated events have been shown to occur on sub-arcsecond
scales, have lifetimes of the order minutes, and to sometimes occur co-spatial to
umbral dots. In this talk, we present an analysis of these jet-like features using a
range of data collected using the Swedish Solar Telescope. Initially, the basic
properties of these events (including lifetimes and sizes) are measured in Ca II H
time-series data before an investigation into their signatures in co-spatial CRisp
Imaging SpectroPolarimeter Ca II 8542 A line scans is conducted. This research
displays links between these micro-jets and a sub-set of dark extensions in the
umbra, potentially similar to dynamic fibrils or umbral spikes. Finally,
spectro-polarimetric measurements are studied allowing some inferences to be made
regarding the local atmospheres surrounding these structures. Overall, this research
provides further evidence for the jet-like nature of umbral micro-jets as well as for
links between these events and at least a sub-set of dark extended structures
observed in Ca II 8542 A line profiles.
Primary author
Christopher Nelson
(University of Sheffield & Queen's University Belfast)
