A study of collisionless particle energization in current sheets: roles of turbulence and magnetic reconnection

The true first state of matter, plasma, is the primary substance that composes nearly all of the visible universe. Plasmas, or ionized gases consisting of charged particles, are ubiquitous throughout nature, and play a pivotal role in the dynamics of many space and astrophysical objects and phenomena. Many plasmas, such as in our Sun, its wind, huge molecular clouds, and galaxies where stars form and die, possess complicated electric and magnetic fields that influence plasma behavior. These electromagnetic fields, unlike in normal fluids or gasses, give plasmas many unique behaviors and impose extra restrictions on their motion and behavior.

The electromagnetic fields and particles within a plasma possess their own energy, magnetic fields possess tension like a string, and particles act like billiard balls that possess kinetic energy, just like molecules in air. To understand how space and astrophysical plasmas evolve, it is helpful to understand how the electromagnetic fields and plasma particles transfer energy to and from each other. Understanding this energy transfer is pivotal to answering questions related to how the Sun emits and transfers the energy produced during nuclear fusion at its core, out to its extremely hot corona, and supersonic wind that pervades the solar system. This understanding can help us predict the impact of space weather from the solar wind, which can harm modern electronics, satellites in orbit, and eventually, interplanetary human travellers.

In this thesis we explore how electromagnetic fields transfer energy to, and heat, plasma particles. We use computational simulations to carryout investigations, that enable new ways of identifying unique signatures of the physical mechanisms responsible for the transfer of energy from electromagnetic fluctuations to heat plasma particles. We investigate energy transfer due to the interactions arising from collisions of Alfvén waves, a fundamental plasma wave that travels along magnetic fields, and due to the reconfiguration of magnetic fields, which can break apart and reform, in a process called magnetic reconnection.