This project aims to better understand an important instability of Alfvén waves in laboratory and space plasmas using computer simulations. Alfvén waves are the most fundamental mode of a plasma in a magnetic field; the behavior of these waves may underpin important questions like why the solar corona is heated to unusually high temperatures and how fusion reactions in a magnetic bottle perform. At high amplitudes, Alfvén waves are unstable and convert into other modes. This process, called a parametric instability, is a possible mechanism that may redistribute energy in both space and fusion plasmas. For example, the ion sound wave produced by the most common type of parametric instability, known as the parametric decay instability (PDI), may heat ions in the plasma. Despite their potential significance, observational evidence of these instabilities in both space and laboratory plasmas is still limited and, sometimes, puzzling. Experiments at the Large Plasma Device (LAPD) at UCLA do not see PDI, but instead see a different parametric instability that has not yet been confirmed in theory or simulations. To better understand these problems and aid future laboratory studies, we propose using particle-in-cell simulations which can model the behavior of individual ions and electrons in the plasma. In previous studies of Alfvén wave parametric instabilities, these kinetic effects are often included only for ions; this is because the wave oscillates orders of magnitude slower than electron’s response time. However, Alfvén waves may directly interact with electrons in many non-idealized laboratory and space scenarios. We will close this gap by developing experiment-relevant features in a fully kinetic particle-in-cell simulation model. The simulations will then be deployed to study parametric instabilities in a uniform low-beta plasma where the magnetic field pressure dominates over the plasma pressure, an important regime relevant to both the solar coronal region and laboratory study. Particular attention will be paid to wave energy partition between electrons and ions and how this affects the instability development. Relevant laboratory data available at LAPD will be leveraged to provide inputs and benchmarks for the computer simulations. Finally, we will briefly explore the effect of a non-uniform magnetic field that has relevance to the solar coronal region. Results from this project are expected to significantly improve our understanding of how Alfvén waves transfer and redistribute their energy in plasma, addressing crucial questions in frontier plasma science. The results will also help clarify the relevance and role of these instabilities to space phenomena and improve large-scale simulation for a range of basic plasma processes. The team includes experts in both computational plasma studies and experimental plasma physics and aims to provide training and mentorship to a junior scientist to prepare them for the STEM workforce.
