English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Super-sonic downflows have been observed in transition region spectra abovenumerous sunspots; however, little research has been conducted to date into howpersistent these signatures are within sunspots on time-scales longer than afew hours. Here, we analyse the lead sunspot of AR 12526 to infer theproperties and evolution of super-sonic downflows occurring within it. Sixteenlarge, dense raster scans sampled by IRIS are analysed. These rasters trackedthe lead sunspot of AR 12526 at discrete times between the 27th March 2016 andthe 2nd April 2016. One sit-and-stare observation acquired on the 1st April2016 is also studied in order to analyse the evolution of super-sonic downflowson shorter time-scales. Super-sonic downflows are variable within this sunspotboth in terms of spatial structuring and velocities. 13 of the 16 raster scansdisplay some evidence of super-sonic downflows in the Si IV 1394 {\AA} lineco-spatial to a sustained bright structure detected in the 1400 {\AA} slit-jawimaging channel, with a peak velocity of 112 km s^{-1} being recorded on the29th March 2016. Evidence for super-sonic downflows in the O IV 1401 {\AA} linewas found in 14 of these rasters, with the spatial structuring differing fromthat inferred from the Si IV 1394 {\AA} line. In the sit-and-stare data, nodual flow is initially detected, however, a super-sonic downflow does developafter 60 minutes. This downflow accelerates from 73 km s^{-1} to close to 80 kms^{-1} in both the Si IV 1394 {\AA} and O IV 1401 {\AA} lines over the courseof 20 minutes before the end of the observation. The morphology of thesedownflows evolved over the course of both hours and days and was oftendifferent in the Si IV 1394 {\AA} and O IV 1401 {\AA} lines. These events werefound co-spatial to a bright region in the core of the Si IV 1394 {\AA} linewhich appeared to form at the foot-points of coronal fan loops.

Evolution Of Super-Sonic Downflows In A Sunspot