Description of the objective:


The fast wind, which does not exhibit strong first ionisation potential (FIP) enhancements, could come directly from the photosphere, from small cool coronal loops and open magnetic funnels (Tu et al., 2005; Schwadron and McComas, 2003) at the base of coronal holes or spicules, which also exhibit small FIP enhancements. Remote observations have revealed many cases of macrospicules undergoing reconnection and erupting within coronal holes (Yamauchi et al., 2005). Do they contribute to the fast solar wind streams? Polar plumes have also long been suspected to be a significant source of fast solar wind (Deforest et al., 1997), as well as polar regions within plumes ("interplume lanes") (Giordano et al., 2000). Micro-streams of plasma originating in the coronal holes may be related to polar plumes (Neugebauer et al., 1995), though evidence for this is controversial (e.g., McComas et al., 1996).  However, the relation could be difficult to observe with Solar Orbiter since large amplitude Alfvénic fluctuations generate micro-streams signals in the fast stream (Matteini et al., 2013).



In order to address this objective, we need to observe if the fast wind comes from the different above sources. This objective can be split into two different observational strategies:

The needed observations include:

Other remarks:


The possible remote sensing targets should include wide regions of well extended coronal holes, as well as smaller regions for focusing on the following:

The SOOP that addresses this objective is L_SMALL_HRES_HCAD_Fast-Wind, which also addresses objective



Tu et al. 2005:



Yamauchi et al. 2005:



Deforest et al. 1997:


Required observations: