Beam driven instabilities in magnetized plasmas

Lead Research Organisation: University of St Andrews
Department Name: Mathematics and Statistics


Electromagnetic radiation is another, broader, name for light, encompassing radio waves through to gamma rays. This proposal intends to investigate the ability of an electron beam gyrating in a fixed magnetic field to interact with an electromagnetic wave, in the microwave part of the spectrum. In certain conditions this interaction can be arranged so that the electrons slow down, and the energy they lose is conserved by an increase in the energy of the wave. This process is effectively LASER action. In particular the project will consider an electron beam where some electrons are very nearly travelling along the magnetic field lines and others are gyrating nearly perpendicularly to it. A new theoretical idea has been proposed as a result of astronomical observations which expects especially high growth rates to occur from this type of electron beam and potentially efficient conversion of the electron energy to wave energy. To evaluate this potential, and the validity of the theoretical idea, the project will conduct an experiment where such a beam will be produced by magnetic compression and the emissions from the beam will be observed for different values of the magnetic field and radiation field distributions. Measurements of the beam current, voltage position and velocity will be compared to the measurements of the amplitude and frequency of the microwave emissions. Theoretical research will also be undertaken to ensure the expected behaviour is compared accurately with the actually realisable experimental geometry. This combined approach of theoretical and experimental investigation will allow the project to compare the experimental results with the predictions of the theoretical model and also with the output of computational simulations, thereby establishing its validity and potential for applications.


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Description The project has looked at plasma instabilities driven by electron beams, providing theoretical support to experimental work carried out at the University of Strathclyde. The experimental observations have confirmed theoretical predictions on the nature of an instability suggested to be the source of auroral kilometric radiation with the work at St Andrews providing input to guide the interpretation of these observations. Studies of cyclotron radiation from inhomogeneous systems have suggested how waves generated in a localised region might propagate out into its surroundings.