Small-scale magnetic flux ropes and their properties based on in-situ measurements from Parker Solar Probe

TL;DR

This study identifies and analyzes small-scale magnetic flux ropes near the Sun using Parker Solar Probe data, revealing their properties, configurations, and potential origins related to solar turbulence and reconnection.

Contribution

First in-depth analysis of small-scale flux ropes with detailed properties and configurations based on Parker Solar Probe in-situ measurements.

Findings

Flux ropes range from 10 seconds to 1 hour in duration.

Most flux ropes propagate anti-sunward with no preferred helicity sign.

Flux function follows a power law proportional to scale size.

Abstract

We report small-scale magnetic flux ropes via the Parker Solar Probe in situ measurements during the first six encounters and present additional analyses to supplement our prior work in Chen et al. 2021. These flux ropes are detected by the Grad-Shafranov-based algorithm with the duration and scale size ranging from 10 seconds to $\lesssim$1 hour and from a few hundred kilometers to 10$^{-3}$ au, respectively. They include both static structures and those with significant field-aligned plasma flows. Most structures tend to possess large cross helicity, while the residual energy distributes in wide ranges. We find that these dynamic flux ropes mostly propagate anti-sunward, with no preferential sign of magnetic helicity. The magnetic flux function follows a power law and is proportional to scale size. We also present case studies showing reconstructed two-dimensional (2D) configurations, which confirm that the static and dynamic flux ropes have the common configuration of spiral magnetic field lines (also streamlines). Moreover, the existence of such events hints at the interchange reconnection as a possible mechanism to generate flux rope-like structures near the Sun. Lastly, we summarize the major findings and discuss the possible correlation between these flux rope-like structures and turbulence due to the process of local Alfvenic alignment.