A parametric study of the numerical simulations of triggered VLF emissions

• Published in: Annales Geophysicae
• Main Authors: D. Nunn, M. Rycroft, V. Trakhtengerts
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2005
• Subjects: Science; Q; Physics; QC1-999; Geophysics. Cosmic physics; QC801-809; Siple; Antarc*; Antarctica
• Online Access: https://doi.org/10.5194/angeo-23-3655-2005; https://doaj.org/article/aafd26995dc9433593ee431985b717bf

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.