Magnetic field amplification in laser-produced plasmas

Thesis

The universe abounds with shock waves, from those arising during structure formation, to those driving supernova explosions that create the elements of which life is made and can even trigger star formation. In the early universe, matter was nearly homogeneously distributed; today, as a result of gravitational instabilities, it forms a web-like structure of clusters, filaments, and voids. Radio-Synchrotron emission and Faraday Rotation measurements have revealed that clusters, filaments, and voids are all magnetised from a few nG to tens of μG. When integrated over the whole universe, this magnetic energy represents a sizeable component of the cosmic energy budget, making magnetic fields essential players in the dynamics of luminous matter in the universe.

At present, the origin and distribution of magnetic fields are far from understood. The standard model for the origin of galactic and intergalactic magnetic fields is through the generation of small seed fields by some mechanism (e.g. Biermann Battery) and the amplification of these seed fields via dynamo or turbulent processes to the level consistent with current observations. Due to the advent of high-powered lasers, scaled astrophysical phenomena can be created in the laboratory - a supernova several parsecs in diameter can be scaled down to the size of a baseball. These laboratory plasmas are similar to plasmas in the universe in terms of localisation, heat conduction, viscosity, and radiation.

Here we report on experimental measurements of magnetic field amplification by turbulent motions in both laser-produced shock waves scaled to supernova remnants and laser-produced jets analogous to cluster merger events. These measurements of turbulent magnetic field amplification in a laser-produced plasma are a precursor to turbulent dynamo [11] in which amplification is no longer limited by diffusion, and a necessary component in explaining the magnetisation of luminous matter in the universe.

Authors: Meinecke, J

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford