Statistical analysis of intermittency and its association with proton heating in the near Sun environment

TL;DR

This study analyzes magnetic structures in the near Sun environment using Parker Solar Probe data, revealing their role in proton heating and turbulence, with smaller, frequent structures contributing significantly to energy dissipation.

Contribution

It introduces a statistical analysis linking magnetic intermittency, characterized by PVI, to proton heating and turbulence dissipation in the inner heliosphere, highlighting the importance of smaller-scale structures.

Findings

Proton heating correlates with magnetic structures having PVI ≥ 1.

Waiting times of structures follow a power-law distribution, indicating clustering.

Small-scale structures (1 < PVI < 6) dominate magnetic energy dissipation.

Abstract

We use data from the first six encounters of Parker Solar Probe and employ the Partial Variance of Increments ($PVI$) method to study the statistical properties of coherent structures in the inner heliosphere with the aim of exploring physical connections between magnetic field intermittency and observable consequences such as plasma heating and turbulence dissipation. Our results support proton heating localized in the vicinity of, and strongly correlated with, magnetic structures characterized by $PVI \geq 1$. We show that on average, such events constitute $\approx 19\%$ of the dataset, though variations may occur depending on the plasma parameters. We show that the waiting time distribution ($WT$) of identified events is consistent across all six encounters following a power-law scaling at lower $WTs$. This result indicates that coherent structures are not evenly distributed in the solar wind but rather tend to be tightly correlated and form clusters. We observe that the strongest magnetic discontinuities, $PVI \geq 6$, usually associated with reconnection exhausts, are sites where magnetic energy is locally dissipated in proton heating and are associated with the most abrupt changes in proton temperature. However, due to the scarcity of such events, their relative contribution to energy dissipation is minor. Taking clustering effects into consideration, we show that smaller scale, more frequent structures with PVI between, $1\lesssim PVI \lesssim 6$, play the major role in magnetic energy dissipation. The number density of such events is strongly associated with the global solar wind temperature, with denser intervals being associated with higher $T_{p}$.