Physical properties of active region upflows

DÉMOULIN, P.; BAKER, D.; JANVIER, M.; MANDRINI, C.H.

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Workshop; 10th Coronal Loops Workshop: 20 years of loops with new insights form Solar Obiter; 2022

Large scale high-speed upflows have been detected by the EUV Imaging Spectrometer (EIS) on-board the Hinode satellite.  These upflows are typically observed by pairs at the following and leading borders of active regions (ARs).  These long-lived upflows are located in regions oflow electron density, low radiance, and over strong magnetic flux concentrations of a singlepolarity. The line-profile blueshifts range from a few to 50 km/s and they are fasterin hotter coronal emission lines.  These properties contrast with the ones of the typically red shifted and dense coronal loops present in AR cores.  The AR loops have a longterm expansion driven by the AR magnetic field emergence, then spreading (due to convective motions).  We conclude that AR upflows are originating from reconnection along quasi-separatrix layers between overpressure AR loops and neighboring underpressure loops.  In particular, this explains why upflows occur in pairs and are long live (months).