PIRSA:13100078

Plasma without Plasma: Exploring Force-Free Magnetospheres

Gralla, S. (2013). Plasma without Plasma: Exploring Force-Free Magnetospheres. Perimeter Institute. https://pirsa.org/13100078

Gralla, Samuel. Plasma without Plasma: Exploring Force-Free Magnetospheres. Perimeter Institute, Oct. 10, 2013, https://pirsa.org/13100078 

          @misc{ pirsa_PIRSA:13100078,
            doi = {10.48660/13100078},
            url = {https://pirsa.org/13100078},
            author = {Gralla, Samuel},
            keywords = {Strong Gravity},
            language = {en},
            title = {Plasma without Plasma: Exploring Force-Free Magnetospheres},
            publisher = {Perimeter Institute},
            year = {2013},
            month = {oct},
            note = {PIRSA:13100078 see, \url{https://pirsa.org}}
          }

Sam Gralla University of Arizona

DOI 10.48660/13100078
Collection
Talk Type Scientific Series
Subject

Abstract

Pulsars have enormous magnetic fields whose energy density dwarfs the rest mass density of their plasma magnetosphere. In this regime of a plasma, the particles drop out of the description, leaving a set of equations for the electromagnetic field alone. This non-linear, deterministic system is known as force-free electrodynamics, and turns out to have some beautiful and bizarre features. I will give a pedagogical introduction to these equations and their role in astrophysics and then discuss our recent contributions. We have taken a geometric viewpoint, using the null structure of spacetime to unify previous exact solutions and discover new ones. We have found non-stationary, non-axisymmetric solutions that describe the outer magnetosphere of pulsars, including those that are accelerated or torqued. We have derived the standard cartoon of the aligned pulsar magnetosphere from an explicit, minimal set of assumptions. Time permitting, I will also discuss some properties of black hole magnetospheres: Blandford-Znajek energy extraction, non-scattering force-free waves, and the no-ingrown-hair theorem.