Laboratory simulations of auroral radio emissions

Sandra L McConville , David C Speirs , Kevin Ronald, Karen Gillespie, Alan D R Phelps , Robert Bingham, Adrian W Cross , Craig W Robertson, Colin G Whyte , Wenlong He, Irena Vorgul, Robert A Cairns, Barry J Kellett

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Experiments have investigated the process of AKR (Auroral Kilometric Radiation)
generation which occurs naturally in the Earth’s polar magnetosphere. Satellites have measured radiation powers ~GW’s polarised in the X-mode, near the electron cyclotron frequency, fce~300kHz, emitted from regions of plasma depletion (the auroral density cavity ~3200km above the Earth’s surface), where npe~106m -3 and fpe~9kHz, giving a ratio fce/fpe ~ 30. The estimated radiation efficiency is ~1% of the precipitated electron kinetic energy. A scaled laboratory experiment replicated this auroral phenomenon by injecting an electron beam through a region of increasing magnetic field [1-3]. This magnetically compresses the electron beam producing a distribution in velocity space suitable for radiation emission.
Results will be presented for two resonant magnetic fields discussing the power of the emitted radiation, efficiency of emission, wave polarisation and spectral content. These results were compared to data obtained using the 2D[3,4] and 3D[5] PiC code KARAT.
Recent experiments investigated the addition of a low temperature, low density
background plasma to improve comparisons to the auroral process. A Penning trap installed into the interaction waveguide of the apparatus provided the means for plasma generation, with fce~5.21GHz close to cut-off for the TE01 mode. A probe was used to characterise the plasma giving measurements of fpe~150-300MHz and density npe~1014-1015 m-3, giving fce/fpe~17-35,
comparable to the magnetospheric value.
Original languageEnglish
Title of host publication38th EPS Conference on Plasma Physics
Publication statusPublished - 2011
Externally publishedYes

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