Radial evolution of the properties of small-scale magnetic flux ropes in the solar wind

Abstract

Small-scale magnetic flux ropes, most with duration ≤ 1 hour at 1 AU, are found to be ubiquitous in the solar wind from in-situ spacecraft measurements. We have built an event database (fluxrope.info) for these structures identified and summarized their main physical properties. Quantitative analysis provided strong evidence in support of the view of their generation through turbulence cascade processes in space plasmas. We extend such analysis to spacecraft measurements at larger radial distances, mainly those from the Ulysses spacecraft mission. We perform comparison of relevant properties of these structures and reveal their radial evolution near the ecliptic plane. Meanwhile we also try to derive, quantitatively, the parameters important for the underlying processes including magnetic reconnection, intrinsic to turbulence cascade, in order to aid in relevant theoretical investigations. We also supplement the largely statistical analysis results with individual case studies to illustrate the process of flux rope merging and associated particle energization signatures through an observational approach. We speculate on the implications of our results and foresee future investigations that can help improve our current understanding of the origin and evolution of these small-scale magnetic flux ropes throughout the heliosphere.