Expansion Properties of Small Flux Ropes Observed by Parker Solar Probe

Abstract Small flux ropes (SFRs) observed in the solar wind are transient magnetic field structures with a strong axial field and helical field lines around the core. How these structures evolve as they propagate in the inner heliosphere is still an open question. In this study, we present a list of 68 SFRs observed by Parker Solar Probe between 2018 October and 2021 August. These SFRs were observed at distances ranging from 0.077 to 0.634 au. We examine the expansion characteristics of these SFRs, including the nondimensional expansion parameter. We find that most of these SFRs show no signs of significant expansion, while a small number show signs of contraction. These results provide new information about the potential origin of these structures and their connection to other coronal and interplanetary transients.