First Apparent Speed Maps of Density Structures in the Solar Corona from 1.2 to 3 R ⊙ Derived from Proba-3/ASPIICS White-light Images

Abstract

Abstract Characterizing the sources and dynamics of solar-wind streams is challenging given the complexity of the magnetized density structures and the absence of speed measurements in the low corona. White-light (WL) coronagraphic observations from the recently launched Proba-3/ASPIICS mission now offer the first opportunity to capture the dynamics of WL coronal structures over an uninterrupted span between 1.2 and 3 R ⊙ over a period of several hours. In this Letter, we use a 5 minute time-differenced wavelet-optimized whitening technique to measure apparent motions of WL density structures in the corona using features measured in height–time plots. These height–time plots are subsequently enhanced using a technique similar to the principle of multiscale Gaussian normalization to automate the detection of these features to produce plane-of-sky apparent speed maps. Application of this technique to the Proba-3/ASPIICS data acquired on 2025 July 16 revealed the presence of outflows, as well as inflows, with average speeds of 100 and −50 km s −1 , respectively. The speed of a coronal mass ejection (CME), its leading edge and its fine scale substructures, which were clearly visible within the field of view, could also be measured. These first apparent speed maps of coronal density structures highlight the currently unsurpassed effectiveness of the Proba-3 mission for the exploration of the origin and evolution of the solar wind. They also provide novel boundary conditions for two- and three-dimensional models of the dynamic corona.