Effects of Turbulent Magnetic Fields on the Transport and Acceleration of Energetic Charged Particles: Numerical Simulations with Application to Heliospheric Physics

TL;DR

This paper uses numerical simulations to study how turbulent magnetic fields influence the transport and acceleration of energetic charged particles, with applications to heliospheric physics and solar energetic particles.

Contribution

It introduces comprehensive numerical models combining particle trajectory integration, hybrid simulations, and stochastic methods to analyze particle acceleration and transport in turbulent magnetic fields.

Findings

Dropouts in particle intensities are rare with the two-component turbulence model.

Particles gain energy through shock reflection and field-line braiding.

Large-scale turbulence enhances electron acceleration at shocks.

Abstract

After introduction we focus on: the transport of charged particles, the acceleration of ions at shocks, and the acceleration of electrons at shocks. Chapter 2 studies the propagation of solar energetic particles(SEPs) in turbulent magnetic fields. Particle trajectories in turbulent magnetic fields are numerically integrated. The turbulence includes a Kolmogorov-like power spectrum containing a broad range of scales. Small-scale variations in particle intensities(dropouts) and velocity dispersions can be reproduced. The result gives a constraint on the error of onset analysis for inferring SEP informations. We find that dropouts are rarely produced using the two-component model(Matthaeus et al., 1990). The result questions the turbulence model. Chapter 3 studies the acceleration of ions. We use 3-D hybrid simulations to study the acceleration of low-energy particles at parallel shocks. We find that particles gain energy by reflection at the shock. The protons can move off field lines in 3-D electric and magnetic fields. We also use a stochastic integration method to study diffusive shock acceleration including large-scale magnetic variations. The results can explain the observations of anomalous cosmic rays by Voyager 1. Chapter 4 studies electron acceleration at a shock in a turbulent magnetic field by combining hybrid simulations and test-particle simulations. The acceleration is enhanced by including large-scale turbulence. Since electrons mainly follow field lines, the field-line braiding allows electrons interacting with shock many times. Ripples also contribute to acceleration by mirroring electrons. The process favors perpendicular shocks. We discuss the implication to SEPs by comparing the acceleration of electrons with that of protons. The intensity correlation of electrons and ions in SEPs implies perpendicular shocks play important roles in accelerating particles.