# GiRaFFE: An Open-Source General Relativistic Force-Free Electrodynamics Code

## TL;DR

GiRaFFE is the first open-source code for simulating force-free electrodynamics in dynamical, relativistic spacetimes, enabling large-scale astrophysical plasma simulations.

## Contribution

It introduces GiRaFFE, a novel open-source GRFFE code based on IllinoisGRMHD, compatible with the Einstein Toolkit for scalable, dynamical spacetime simulations.

## Key findings

- Successfully passes flat and curved spacetime tests
- Compatible with adaptive-mesh refinement grids
- Ready for large-scale astrophysical simulations

## Abstract

We present GiRaFFE, the first open-source general relativistic force-free electrodynamics (GRFFE) code for dynamical, numerical-relativity generated spacetimes. GiRaFFE adopts the strategy pioneered by McKinney and modified by Paschalidis and Shapiro to convert a GR magnetohydrodynamic (GRMHD) code into a GRFFE code. In short, GiRaFFE exists as a modification of IllinoisGRMHD, a user-friendly, open-source, dynamical-spacetime GRMHD code. Both GiRaFFE and IllinoisGRMHD leverage the Einstein Toolkit's highly-scalable infrastructure to make possible large-scale simulations of magnetized plasmas in strong, dynamical spacetimes on adaptive-mesh refinement (AMR) grids. We demonstrate that GiRaFFE passes a large suite of both flat and curved-spacetime code tests passed by a number of other state-of-the-art GRFFE codes, and is thus ready for production-scale simulations of GRFFE phenomena of key interest to relativistic astrophysics.