Magnetic effects in astrophysically relevant laboratory plasmas

Thesis

Astrophysics typically uses observation, theory and simulation to further the understanding of the cosmos. By using high power lasers, scaled astrophysical events can be created in the laboratory.

This thesis describes laboratory results based on two different astrophysical phenomena, particle acceleration and the turbulent dynamo mechanism, both of which are governed by magnetic fields.

Particle acceleration is commonly seen at astrophysical shocks. The exact mechanism of this acceleration, especially for electrons, remains unclear. One possible method of electron acceleration is through lower hybrid turbulence, a phenomena observed at the interaction between the Solar wind and a comet. The results from a laboratory experiment demonstrate the observation of electron acceleration via lower hybrid waves. Lower hybrid waves require an external magnetic field to generate the necessary electron accelerating instability.

Magnetic fields themselves are ubiquitous throughout the universe. Having generated seed fields through, for example an astrophysical shock, these magnetic fields can be ampliflied through the turbulent dynamo mechanism. To generate the dynamo mechanism within the laboratory, two plasma jets are collided. A new Faraday rotation diagnostic, for magnetic field measurements, was added to the suite of diagnostics characterizing the turbulent plasma. The setup, calibration and analysis for the Faraday rotation diagnostic is new to the OMEGA laser facility and dynamo experiment. The results from this new Faraday rotation diagnostic and Thomson scattering diagnostic allow the plasma parameters and evolution of the jets to be fully characterized.

Finally, the thesis is concluded by drawing these results together.

Authors: Rigby, A

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