Parallel Evolution of Quasi-separatrix Layers and Active Region Upflows

MANDRINI, C.H.; BAKER, D.; DÉMOULIN, P.; CRISTIANI, G.; VAN DRIEL-GESZTELYI, L.; VARGAS DOMÍNGUEZ, S.; NUEVO, F.A.; VÁSQUEZ, A.M.; PICK, M.

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2015 vol. 809

0004-637X

Persistent plasma upflows were observed with Hinode´s EUV ImagingSpectrometer (EIS) at the edges of active region (AR) 10978 as itcrossed the solar disk. We analyze the evolution of the photosphericmagnetic and velocity fields of the AR, model its coronal magneticfield, and compute the location of magnetic null-points andquasi-sepratrix layers (QSLs) searching for the origin of EIS upflows.Magnetic reconnection at the computed null points cannot explain all ofthe observed EIS upflow regions. However, EIS upflows and QSLs are foundto evolve in parallel, both temporarily and spatially. Sections of twosets of QSLs, called outer and inner, are found associated to EIS upflowstreams having different characteristics. The reconnection process inthe outer QSLs is forced by a large-scale photospheric flow patternwhich is present in the AR for several days. We propose a scenario inwhich upflows are observed provided a large enough asymmetry in plasmapressure exists between the pre-reconnection loops and for as long as aphotospheric forcing is at work. A similar mechanism operates in theinner QSLs, in this case, it is forced by the emergence and evolution ofthe bipoles between the two main AR polarities. Our findings providestrong support to the results from previous individual case studiesinvestigating the role of magnetic reconnection at QSLs as the origin ofthe upflowing plasma. Furthermore, we propose that persistentreconnection along QSLs does not only drive the EIS upflows, but it isalso responsible for a continuous metric radio noise-storm observed inAR 10978 along its disk transit by the Nanc{c}ay Radio Heliograph.