Persistence of magnetic field driven by relativistic electrons in a plasma

TL;DR

This paper demonstrates a new mechanism where ultra-energetic particles generate strong magnetic fields at plasma boundaries, confirmed by experiments and simulations, advancing understanding of magnetic field origins in plasma physics.

Contribution

The study reveals a novel particle-driven magnetic field generation mechanism in plasmas, validated through large-scale measurements and simulations.

Findings

Magnetic fields up to 100 Tesla observed at plasma boundaries.

First time-resolved measurements in laser wakefield accelerators.

Simulations confirm experimental results and mechanism.

Abstract

The onset and evolution of magnetic fields in laboratory and astrophysical plasmas is determined by several mechanisms, including instabilities, dynamo effects and ultra-high energy particle flows through gas, plasma and interstellar-media. These processes are relevant over a wide range of conditions, from cosmic ray acceleration and gamma ray bursts to nuclear fusion in stars. The disparate temporal and spatial scales where each operates can be reconciled by scaling parameters that enable to recreate astrophysical conditions in the laboratory. Here we unveil a new mechanism by which the flow of ultra-energetic particles can strongly magnetize the boundary between the plasma and the non-ionized gas to magnetic fields up to 10-100 Tesla (micro Tesla in astrophysical conditions). The physics is observed from the first time-resolved large scale magnetic field measurements obtained in a laser wakefield accelerator. Particle-in-cell simulations capturing the global plasma and field dynamics over the full plasma length confirm the experimental measurements. These results open new paths for the exploration and modelling of ultra high energy particle driven magnetic field generation in the laboratory.