Identification of Magnetic Flux Ropes from Parker Solar Probe Observations during the First Encounter

TL;DR

This paper analyzes Parker Solar Probe data to identify large and small-scale magnetic flux ropes using wavelet analysis, revealing their properties and potential roles in solar wind turbulence and coronal heating.

Contribution

It introduces a wavelet-based method to detect and characterize magnetic flux ropes at multiple scales in the solar wind from PSP observations.

Findings

ICME as a magnetic flux rope with high magnetic helicity and low cross helicity

Identification of small-scale flux ropes with durations from 8 to 300 minutes

Small flux ropes may contribute to particle acceleration and coronal heating

Abstract

The Parker Solar Probe (PSP) observed an interplanetary coronal mass ejection (ICME) event during its first orbit around the sun, among many other events. This event is analyzed by applying a wavelet analysis technique to obtain the reduced magnetic helicity, cross helicity, and residual energy, the first two of which are magnetohydrodynamics (MHD) invariants. Our results show that the ICME, as a large scale magnetic flux rope, possesses high magnetic helicity, very low cross helicity, and highly negative residual energy, thus pointing to a magnetic fluctuation dominated structure. Using the same technique, we also search for small-scale coherent magnetic flux rope structures during the period from 2018/10/22--2018/11/21, which are intrinsic to quasi-2D MHD turbulence in the solar wind. Multiple structures with duration between 8 and 300 minutes are identified from PSP in-situ spacecraft measurements. The location and scales of these structures are characterized by wavelet spectrograms of the normalized reduced magnetic helicity, normalized cross helicity and normalized residual energy. Transport theory suggests that these small-scale magnetic flux ropes may contribute to the acceleration of charged particles through magnetic reconnection processes, and the dissipation of these structures may be important for understanding the coronal heating processes.