Ubiquitous Small-scale Dynamics in the Slow Solar Wind Formation Region Observed by Proba-3/ASPIICS

Abstract The origin of the slow solar wind remains a subject of ongoing debate. Several mechanisms have been proposed: the large expansion factor of open magnetic field in the corona, interchange reconnection between open and closed field lines in streamers and pseudostreamers, reconnection within the web of separatrices (S-web), and the field line pinch-off at streamer cusps. Many of these mechanisms involve the release of small-scale density inhomogeneities into the solar wind. A significant obstacle to understanding these processes is the difficulty of observing the region between the lower corona (traditionally observed with extreme ultraviolet imagers) and the high corona (traditionally observed with externally occulted coronagraphs), where these small-scale structures are thought to originate. Here, we present for the first time high-cadence (30 s) and high-spatial-resolution (5 . ″ 6) white-light observations of the solar corona in the range of the radial distances r of 1.1 R ⊙ < r < 3 R ⊙ taken by the ASPIICS coronagraph on board the formation-flying Proba-3 mission. The ASPIICS data reveal ubiquitous, weak (0.5%–2% of the background brightness), small-scale dynamic features (blobs, outflows, inflows, jets, and waves). Their speeds range from 14 km s −1 to 520 km s −1 , with outflowing structures generally propagating faster than the inflowing ones. All these features appear to originate from streamers and pseudostreamers. ASPIICS observations provide important constraints on the role of small-scale dynamics in the formation of the slow solar wind.