Linear self-focusing of whistlers in plasmas

We present theoretical and simulation studies of the linear self-focusing of frequency modulated electron whistlers in plasmas. A comparison has been made between analytical results of a wave-kinematic model and a direct simulation of the whistler wave equation. The self-focusing of whistlers comes about due to the specific form of the whistler mode dispersion, which allows the whistler wave energy to be transported at different speeds for waves with different wavelengths, and where the waves with larger group speeds overtake waves with lower speeds. Our numerical results are also compared with recent experiments, which report the frequency-modulated whistlers and their rapid localization in plasmas.