Apparent and Intrinsic Evolution of Active Region Upflows

Abstract

We analyze the evolution of Fe XII coronal plasma upflows from the edges of ten active regions (ARs) as they cross the solar disk using the Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) to do this. Confirming the results of Démoulin et al. (Sol. Phys. 283, 341, 2013), we find that for each AR there is an observed long-term evolution of the upflows. This evolution is largely due to the solar rotation that progressively changes the viewpoint of dominantly stationary upflows. From this projection effect, we estimate the unprojected upflow velocity and its inclination to the local vertical. AR upflows typically fan away from the AR core by 40°to nearly vertical for the following polarity. The span of inclination angles is more spread out for the leading polarity, with flows angled from −29°(inclined toward the AR center) to 28°(directed away from the AR). In addition to the limb-to-limb apparent evolution, we identify an intrinsic evolution of the upflows that is due to coronal activity, which is AR dependent. Furthermore, line widths are correlated with Electronic supplementary material The online version of this article

Helium abundance and speed difference between helium ions and protons in the solar wind from coronal holes, active regions, and quiet Sun

“…Spectroscopic observations have shown that there exists a stable outflow at the base of CH regions (Hassler et al 1999;Xia et al 2003Xia et al , 2004Tu et al 2005) and the outflow usually corresponds to concentrations of unipolar magnetic fields (Xia et al 2003(Xia et al , 2004 where the open magnetic field lines are rooted. On the other hand, closed loops dominate in ARs and QS, and therefore, the solar wind plasma is more likely to be released by magnetic reconnection between closed loops and open magnetic field lines (Neugebauer et al 2002;Feldman et al 2005;Harra et al 2008;He et al 2010;Zangrilli & Poletto 2012;van Driel-Gesztelyi et al 2012;Culhane et al 2014;Mandrini et al 2014;Baker et al 2017).…”

“…Bryans et al (2010) established that the outflows can be present for several days and also identified multiple velocity components in the EIS Fe xii and Fe xiii lines of up to 200 km s −1 . The follow-up finding of upflows at heights between 1.5 and 2.5 R ⊙ in the solar atmosphere using data from the Ultra-Violet Coronagraph Spectrometer on board SoHO in the H i Ly α and O vi doublet lines at 1031.9Å and 1037.6Å (Zangrilli & Poletto 2012) further supported the evidence that AR peripheries are a possible source of the slow SW. Several studies followed investigating both observationally and through modelling the association of AR upflows with the solar wind (He et al 2010;van Driel-Gesztelyi et al 2012;Culhane et al 2014;Mandrini et al 2014;Brooks et al 2015;Galsgaard et al 2015;Vanninathan et al 2015;Zangrilli & Poletto 2016;Baker et al 2017).…”

Widespread occurrence of high-velocity upflows in solar active regions

“…Furthermore, since observing the emergence phase is difficult, the formation of the upflows is often missed. If this is a quick process, it might well be the case that upflows exist for most of the lifetime of an AR (Démoulin et al 2013;Zangrilli & Poletto 2016;Baker et al 2017;Harra et al 2017).…”

Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope

“…These large-scale and steady bulk plasma flows are localized at the following and leading sides of active regions with each upflow area associated with a magnetic monopolar field, which can be a sunspot or multiple flux tubes of the same polarity (more typical for the following polarity). Upflows are observed to occur in pairs, whether as a single pair in isolated bipolar active regions, or as multiple pairs in more complex configurations (Baker et al, 2017). The magnitude of the velocities observed in strong coronal emission lines, such as Fe XII 195.12 Å and Fe XIII 202.04 Å, is in the range of [5,50] km s −1 when fitted with single Gaussian functions (e.g.…”