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

TL;DR

This paper introduces a new method combining magnetic helicity and PVI to identify magnetic structures in space plasmas, validated through simulations and applied to Parker Solar Probe data, revealing flux tubes and reconnection regions.

Contribution

The paper presents a novel single-spacecraft technique combining magnetic helicity and PVI for identifying multi-scale magnetic structures in space plasmas.

Findings

Identification of numerous flux tubes in the solar wind.

Detection of regions where magnetic reconnection and particle acceleration occur.

Validation of the method with numerical simulations and spacecraft data.

Abstract

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