3D PiC code investigations of auroral kilometric radiation mechanisms

Gillespie, K. M. and McConville, S. L. and Speirs, D. C. and Ronald, K. and Phelps, A. D R and Bingham, R. and Cross, A. W. and Robertson, C. W. and Whyte, C. G. and He, W. and Vorgul, I. and Cairns, R. A. and Kellett, B. J. (2014) 3D PiC code investigations of auroral kilometric radiation mechanisms. Journal of Physics: Conference Series, 511 (1). ISSN 1742-6588

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    Abstract

    Efficient (∼1%) electron cyclotron radio emissions are known to originate in the X mode from regions of locally depleted plasma in the Earths polar magnetosphere. These emissions are commonly referred to as the Auroral Kilometric Radiation (AKR). AKR occurs naturally in these polar regions where electrons are accelerated by electric fields into the increasing planetary magnetic dipole. Here conservation of the magnetic moment converts axial to rotational momentum forming a horseshoe distribution in velocity phase space. This distribution is unstable to cyclotron emission with radiation emitted in the X-mode. Initial studies were conducted in the form of 2D PiC code simulations [1] and a scaled laboratory experiment that was constructed to reproduce the mechanism of AKR. As studies progressed, 3D PiC code simulations were conducted to enable complete investigation of the complex interaction dimensions. A maximum efficiency of 1.25% is predicted from these simulations in the same mode and frequency as measured in the experiment. This is also consistent with geophysical observations and the predictions of theory.