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 Plus annual

Presents the access of premium content as premium feature

Premium Content

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 annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We analyze the evolution of Fe XII coronal plasma upflows from the edges often active regions (ARs) as they cross the solar disk using the Hinode ExtremeUltraviolet Imaging Spectrometer (EIS). Confirming the results of Demoulin etal. (2013, Sol. Phys. 283, 341), we find that for each AR there is an observedlong term evolution of the upflows which is largely due to the solar rotationprogressively changing the viewpoint of dominantly stationary upflows. Fromthis projection effect, we estimate the unprojected upflow velocity and itsinclination to the local vertical. AR upflows typically fan away from the ARcore by 40 deg. to near vertical for the following polarity. The span ofinclination angles is more spread for the leading polarity with flows angledfrom -29 deg. (inclined towards the AR center) to 28 deg. (directed away fromthe AR). In addition to the limb-to-limb apparent evolution, we identify anintrinsic evolution of the upflows due to coronal activity which is ARdependent. Further, line widths are correlated with Doppler velocities only forthe few ARs having the largest velocities. We conclude that for the line widthsto be affected by the solar rotation, the spatial gradient of the upflowvelocities must be large enough such that the line broadening exceeds thethermal line width of Fe XII. Finally, we find that upflows occurring in pairsor multiple pairs is a common feature of ARs observed by Hinode/EIS, with up tofour pairs present in AR 11575. This is important for constraining the upflowdriving mechanism as it implies that the mechanism is not a local one occurringover a single polarity. AR upflows originating from reconnection alongquasi-separatrix layers (QSLs) between over-pressure AR loops and neighboringunder-pressure loops is consistent with upflows occurring in pairs, unlikeother proposed mechanisms acting locally in one polarity.

Apparent and Intrinsic Evolution of Active Region Upflows