Collaborative Research: Effects of the Magnetic Field Shear and Flow Shear on Kinetic Physics in Relativistic Magnetic Reconnection

Dartmouth College, Hanover NH

Investigators

Abstract

Magnetic reconnection is a fundamental plasma process, where a change in the connectivity of magnetic field lines rapidly converts energy of the magnetic field into acceleration of charged particles in the plasma. This project aims to improve our understanding of relativistic magnetic reconnection in astrophysical systems. Prompted by the observation of superflares in the Crab Nebula, over the past five years there has been a surge of interests in relativistic reconnection in the high-energy astrophysics community. However, the rich physics of high energy magnetic reconnection and its associated particle acceleration remain less studied compared to their non-relativistic counterparts in Earth's magnetosphere and solar wind. This project will serve to cross-fertilize understanding of magnetic reconnection between the heliophysics and astrophysics communities, which in turn will help develop new insights into this fundamental process and its potential applications. The research activity will include training of students and a postdoc at Dartmouth College and a summer student intern through the New Mexico Consortium. In astrophysical systems such as pulsar wind nebulae and relativistic jets associated with gamma-ray bursts and black holes, the magnetic energy density is much greater than the plasma energy density. In such strongly magnetized plasmas, outflow speed from magnetic reconnection events can reach values close to the speed of light with relativistic effects becoming important. In a realistic system, magnetic reconnection is also often accompanied by finite guide fields and flow shear. A guide field can reduce the reconnection outflow speed, while a shear flow can couple reconnection with flow vortices to affect plasma transport and energy dissipation. It is thus imperative to study and identify how special relativity can affect the dynamics of reconnection under these general conditions. To obtain a self-consistent picture of particle acceleration and to resolve the dissipation-scale physics that breaks the magnetic connectivity, the project will employ a state-of-the-art particle-in-cell code VPIC and provide a fully kinetic description of collisionless magnetic reconnection in the relativistic regime. The results of this study will be relevant for many astrophysical sources and will address the goals of NSF's "Windows on the Universe: The Era of Multi-Messenger Astrophysics" Big Idea. This project is jointly supported by the Division of Physics and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.