Magnetic topology of active regions and coronal holes: Implications for coronal outflows and the solar wind

VAN DRIEL-GESZTELYI, L.; CULHANE, J.L.; BAKER, D.; DÉMOULIN, P.; MANDRINI, C.H.; DEROSA, M.L.; ROUILLARD, A.P.; OPITZ, A.; STENBORG, G.; VOURLIDAS, A.; BROOKS, D.H.

SOLAR PHYSICS

SPRINGER

Lugar: Berlín; Año: 2012 vol. 281 p. 237 - 262

0038-0938

During 2 - 18 January 2008 a pair of low-latitude opposite-polarity coronal holes (CHs) were observed on the Sun with two active regions (ARs) and the heliospheric plasma sheet located between them. We use the Hinode/EUV Imaging Spectrometer (EIS) to locate AR-related outflows and measure their velocities. Solar-Terrestrial Relations Observatory (STEREO) imaging is also employed, as are the Advanced Composition Explorer (ACE) in-situ observations, to assess the resulting impacts on the solar wind (SW) properties. Magnetic-field extrapolations of the two ARs confirm that AR plasma outflows observed with EIS are co-spatial with quasi-separatrix layer locations, including the separatrix of a null point. Global potential-field source-surface modeling indicates that field lines in the vicinity of the null point extend up to the source surface, enabling a part of the EIS plasma upflows access to the SW. We find that similar upflow properties are also observed within closed-field regions that do not reach the source surface. We conclude that some of plasma upflows observed with EIS remain confined along closed coronal loops, but that a fraction of the plasma may be released into the slow SW. This suggests that ARs bordering coronal holes can contribute to the slow SW. Analyzing the in-situ data, we propose that the type of slow SW present depends on whether the AR is fully or partially enclosed by an overlying streamer.