Biermann-battery driven magnetized collisionless shock precursors in laser produced plasmas

TL;DR

This study presents the first experimental observation of magnetized collisionless shock precursors in laser-produced plasmas, demonstrating the role of Biermann-battery magnetic fields in shock formation and electron acceleration.

Contribution

It provides the first complete observation and simulation of magnetized collisionless shock precursors driven by Biermann-battery magnetic fields in laser plasmas.

Findings

Collisionless shock precursors confirmed by Thomson scattering.

Electrons accelerated up to 100 keV with a power-law spectrum.

Magnetohydrodynamic and particle-in-cell simulations support experimental results.

Abstract

This letter reports the first complete observation of magnetized collisionless shock precursors formed through the compression of Biermann-battery magnetic fields in laser produced plasmas. At OMEGA, lasers produce a supersonic CH plasma flow which is magnetized with Biermann-battery magnetic fields. The plasma flow collides with an unmagnetized hydrogen gas jet plasma to create a magnetized shock precursor. The situation where the flowing plasma carries the magnetic field is similar to the Venusian bow shock. Imaging 2$\omega$ Thomson scattering confirms that the interaction is collisionless and shows density and temperature jumps. Proton radiographs have regions of strong deflections and FLASH magnetohydrodynamic (MHD) simulations show the presence of Biermann fields in the Thomson scattering region. Electrons are accelerated to energies of up to 100 keV in a power-law spectrum. OSIRIS particle-in-cell (PIC) simulations, initialized with measured parameters, show the formation of a magnetized shock precursor and corroborate the experimental observables.