The generation of upstream-propagating waves in astrophysically-relevant laboratory plasmas

• Main Author: Crowston, Robert
• Other Authors: Woolsey, Nigel
• Published: University of York 2015
• Subjects: 530
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677380

The primary focus in this thesis is on the production and detection of upstream-propagating waves in laser-laboratory plasmas. Upstream waves are a feature of shocks in plasmas; launched at or just ahead of the shock, they travel against the flow into the unshocked medium. Despite the importance of upstream waves in understanding the properties of the Earth’s bow shock, and the foreshock region just ahead of the shock, upstream waves have not previously been investigated in the laboratory. The laboratory shock waves are produced by laser-matter interaction, and allowed to propagate into a nitrogen atmosphere, immersed in a magnetic field. One-dimensional numerical simulations of the fluid enable the construction of the whistler dispersion function; a mode unstable to growth is identified. The mode is compared with observations taken by a magnetic field probe, understood by a wavelet analysis. Agreement between observation and prediction is found.