UCLA

Magnetic fields are ubiquitous throughout the universe, but the origin of cosmic and galactic magnetic fields is still under investigation. One theorized source of cosmic magnetic seed fields, which also occurs in many astrophysical and laboratory plasma environments, is the Biermann battery effect. This is a thermoelectric effect that spontaneously generates magnetic fields due to non-parallel electron temperature and density gradients in a plasma. In this dissertation, we present high repetition rate, three-dimensional investigations of the Biermann battery effect in laser-generated plasmas and laser-driven hydrodynamic shock waves. Magnetic field measurements revealed azimuthally symmetric magnetic fields reaching values up to 60 G in vacuum and up to 350~G in the presence of laser-driven Sedov-Taylor shock waves. Two-dimensional Thomson scattering measurements of electron temperature and density in laser-driven shock waves revealed electron temperatures up to 25~eV and electron densities up to $2\times 10^{16}$~$cm^{-3}$. 2D Thomson scattering measurements were used to obtain the novel measurements of electron temperature and density gradients within a plasma. The gradients were used to calculate a theoretical value of the Biermann fields due to the laser-driven shock waves, which was in general agreement with the experimental measurements, confirming that magnetic fields are generated by shock waves. Preliminary uncalibrated 3D FLASH simulations were generally in agreement with the experiments, from which we conclude that the majority of the fields measured in the shock waves are due to magnetic field generation by the Biermann battery effect. Dimensionless parameters were used to compare the laboratory experiments with astrophysical systems. The Reynolds and magnetic Reynolds numbers in the shock fronts were found to be much larger than unity, as in many astrophysical systems. A comparison of the experimental $R_m$ and $R_e$ with several astrophysical systems revealed that our experiments may be relevant to supernova remnant shocks, stellar atmospheres, and protogalactic and primordial magnetic field generation.