Variability in the Propagation Characteristics of Small Transients in the Near-Sun Solar Wind Identified by the CORAR Technique

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Abstract Using the Correlation-Aided Reconstruction (CORAR) technique, we identified a population of small transient structures in the near-Sun solar wind observed by the white-light coronagraphs on board STEREO between 2009 December and 2010 September. After excluding partial structures of large-scale coronal mass ejections (CMEs), we manually classified the remaining events into two distinct types: CME-related and CME-unrelated events, and systematically analyzed differences in their propagation characteristics. We find that CME-related events exhibit relatively higher propagation velocities than CME-unrelated events at the same heliocentric distance, and tend to maintain acceleration at greater distances. Additionally, the propagation speeds of CME-unrelated events within different ranges of θ HCS (the angular distance from the heliospheric current sheet, HCS) exhibit comparable magnitudes, suggesting that the empirical relationship between θ HCS and heliospheric solar wind speed is not applicable to the near-HCS transient outflows in the extended corona. We discuss the factors contributing to different propagation behaviors of these small events, as well as their underlying mechanisms, and provide a valuable comparison between the observations and the solar wind simulation by the Magnetohydrodynamic Algorithm outside a Sphere (MAS) coronal model. This work advances our understanding of the origin and evolution of different solar wind transients. It provides unique insights into the transition of released outflows from the Sun to interplanetary solar wind, which is significant for the improvement of solar wind models and coronal simulations.

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