A new method to identify flux ropes in space plasmas

Shiyong Huang,Xiaohua Deng,James Burch,Huishan Fu,Xiongdong Yu,Roy Torbert,Ye Pang,Zhigang Yuan,Haimeng Li,Pufan Zhao,Dedong Wang,Meng Zhou,Jiansen He

doi:10.5194/angeo-36-1275-2018

Abstract

Abstract. Flux ropes are frequently observed in the space plasmas, such as solar wind, planetary magnetosphere and magnetosheath etc., and play an important role in the reconnection process and mass and flux transportation. One usually uses bipolar signature and strong core field to identify the flux ropes. We propose here one new method to identify flux ropes based on the correlations between the variables of the data from in situ spacecraft observations and the “target function to be correlated” (TFC) from the ideal flux rope model. Through comparing the correlation coefficients of different variables at different times and scales, and performing weighted-average techniques, this method can derive the scales and locations of the flux ropes. We compare it with other methods and also discuss the limitation of our method.

Highlights

Magnetic flux ropes, as one universal structure in the space plasma, are formed as a helical magnetic structure with magnetic field lines wrapping and rotating around a central axis (e.g., Hughes and Sibeck, 1987; Slavin et al, 2003; Zong et al, 2004; Zhang et al, 2010)
Flux ropes embedded in current sheet are characterized by the bipolar signature of the normal component of a magnetic field, strong core field in the axis direction and enhancement in magnetic field strength
To identify flux rope only using the magnetic field data from a single spacecraft, we propose a new and simple method based on the correlation coefficients between the signal and the ideal model of flux rope to identify flux ropes in space plasmas

Summary

Introduction

As one universal structure in the space plasma, are formed as a helical magnetic structure with magnetic field lines wrapping and rotating around a central axis (e.g., Hughes and Sibeck, 1987; Slavin et al, 2003; Zong et al, 2004; Zhang et al, 2010). Flux ropes play important roles in dissipating magnetic energy and controlling the microscale dynamics of magnetic reconnection (e.g., Drake et al, 2006; Daughton et al, 2007; Wang et al, 2016; Fu et al, 2017) These structures have been frequently observed and widely studied recently in the magnetosphere, magnetosheath and solar wind (e.g., Hu and Sonnerup, 2001; Slavin et al, 2003; Zong et al, 2004; Zhang et al, 2010; Huang et al, 2012, 2014a, b, 2015, 2016a, b; Rong et al, 2013). S. Huang et al.: A new method to identify flux ropes in space plasmas tions of the shocked solar wind.

Approach

Model test

Flux rope in the magnetosheath

Flux rope in the magnetotail

Findings

Summary and discussion