On the Identification of Coherent Structures in Space Plasmas: the Magnetic Helicity-PVI Method

Plasma turbulence can be viewed as a magnetic landscape populated by largeand small scale coherent structures. In this complex network, large helicalmagnetic tubes might be separated by small scale magnetic reconnection events(current sheets). However, the identification of these magnetic structures in acontinuous stream of data has always been a challenging task. Here we present amethod that is able to characterize both the large and small scale structuresof the turbulent solar wind, based on the combined use of a filtered magnetichelicity ($H_m$) and the Partial Variance of Increments (PVI). This simple,single-spacecraft technique, has been validated first via direct numericalsimulations of plasma turbulence and then applied to data from the Parker SolarProbe (PSP) mission. This novel analysis, combining $H_m$&PVI methods, revealsthat a large number of flux tubes populate the solar wind and continuouslymerge in contact regions where magnetic reconnection and particle accelerationmay occur.