The Temperature, Electron, and Pressure Characteristics of Switchbacks: Parker Solar Probe Observations

TL;DR

This study analyzes Parker Solar Probe data to understand the thermal, electron, and pressure properties of magnetic switchbacks in the solar wind, revealing insights into their structure, heating mechanisms, and pressure balance.

Contribution

It provides detailed observations of thermal states, electron distributions, and pressure signatures inside and outside switchbacks, highlighting new aspects of their physical nature.

Findings

Proton temperature anisotropies vary between regions within switchbacks.

Electrons are more isotropic inside switchbacks, indicating strong scattering.

Switchbacks are pressure-balanced magnetic structures.

Abstract

Parker Solar Probe (PSP) observes unexpectedly prevalent switchbacks, which are rapid magnetic field reversals that last from seconds to hours, in the inner heliosphere, posing new challenges to understanding their nature, origin, and evolution. In this work, we investigate the thermal states, electron pitch angle distributions, and pressure signatures of both inside and outside switchbacks, separating a switchback into spike, transition region (TR), and quiet period (QP). Based on our analysis, we find that the proton temperature anisotropies in TRs seem to show an intermediate state between spike and QP plasmas. The proton temperatures are more enhanced in spike than in TR and QP, but the alpha temperatures and alpha-to-proton temperature ratios show the opposite trends, implying that the preferential heating mechanisms of protons and alphas are competing in different regions of switchbacks. Moreover, our results suggest that the electron integrated intensities are almost the same across the switchbacks but the electron pitch angle distributions are more isotropic inside than outside switchbacks, implying switchbacks are intact structures but strong scattering of electrons happens inside switchbacks. In addition, the examination of pressures reveals that the total pressures are comparable through an individual switchback, confirming switchbacks are pressure-balanced structures. These characteristics could further our understanding of ion heating, electron scattering, and the structure of switchbacks.