3D acceleration of small solar wind tracers and their location origin

To shed light into the physical mechanisms behind the generation/propagation of the slow solar wind, we have studied the kinematics of small-scale structures embedded in the continuously expanding white-light solar corona (i.e., the so-called "blobs" as defined in Sheeley et al., 1997) during the extended past solar minimum and the beginning of the ascending phase of solar cycle 24. The scarce presence of coronal mass ejection events during the selected periods has permitted the identification and individualization of around 100 blob-like structures on the LASCO and SECCHI coronagraphs on board SOHO and STEREO missions, respectively, which in turn allowed us to estimate their un-projected trajectories between 2 and 15 solar radii. Two different methodologies were employed for such an endeavor: (1) A tie-pointing technique, as described in Thompson (2008), and (2) an analysis based on the construction of Height-Time (HT) plots from vantage observing points (Mierla et al., 2008). In agreement with the idea that the blobs are liberated from the cusps of helmet steamers (Wang et al., 1998) and considering their latitudinal distribution during the selected periods of observation in our analysis, we constrained the observing region of interest in the coronagraphs field of view to ×30° from the Sun's equator. As these blobs are indeed reliable white-light tracers of the slow solar wind (Sheeley et al., 1997), we considered long periods (around 5 days) of continuous blobs detachments to explore their sources. We inferred their source locations with the help of the solar magnetic field configuration close to the Sun's surface, using the tridimensional potential field source surface model (PFSS) package developed by De Rosa (2010). The result shows that the source locations of the blobs detachments are close to the tips of the helmet streamers, nearby solar equatorial latitudes as already suggested by Wang et al. (1998). Our results support previous findings that track down the origin of the slow solar wind to neighboring regions of helmet streamers (Habbal et al., 1997).