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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 23, issue 12
Ann. Geophys., 23, 3655–3666, 2005
https://doi.org/10.5194/angeo-23-3655-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 3655–3666, 2005
https://doi.org/10.5194/angeo-23-3655-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  23 Dec 2005

23 Dec 2005

A parametric study of the numerical simulations of triggered VLF emissions

D. Nunn1, M. Rycroft2, and V. Trakhtengerts3 D. Nunn et al.
  • 1School of Electronics and Computer Science, Southampton University, Southampton SO17 1BJ, UK
  • 2CAESAR Consultancy, 35 Millington Rd., Cambridge CB3 9HW, UK
  • 3Institute of Applied Physics, 46 Ulyanov St., Nizhni Novgorod 603950, Russia

Abstract. This work is concerned with the numerical modelling of VLF emissions triggered in the equatorial region of the Earth's magnetosphere, using a well established 1-D Vlasov Hybrid Simulation (VHS) code. Although this code reproduces observed ground based emissions well there is some uncertainty regarding the magnitude of simulation parameters such as saturation wave amplitude, cold plasma density, linear growth rate and simulation bandwidth. Concentrating on emissions triggered by pulses of VLF radio waves from the transmitter at Siple Station, Antarctica (L=4.2), these parameters, as well as triggering pulse length and amplitude, are systematically varied. This parametric study leads to an understanding of the physics of the triggering process and also of how the properties of these emissions, particularly their frequency time profile, depend upon these parameters. The main results are that weak power input tends to generate fallers, intermediate power input gives stable risers and strong growth rates give fallers, hooks or oscillating tones. The main factor determining the frequency sweep rate - of either sign - turns out to be the cold plasma density, lower densities giving larger sweep rates.

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