Effect of frequency modulation on whistler mode waves in the magnetosphere

[1] We present results from numerical studies of whistler mode wave propagation in the Earth’s magnetosphere. Numerical simulations, based on the novel algorithm, solving one-dimensional electron-MHD equations in the dipole coordinate system, demonstrate that the amplitude (and power) of the whistler mode waves generated by the ground-based transmitter can be significantly increased in some particular location along the magnetic field line (for example, at the equatorial magnetosphere) by the frequency modulation of the transmitted signal. The location where the amplitude of the signal reaches its maximum is defined by the time delay between different frequency components of the signal. Simulations reveal that a whistler mode wave with a discrete frequency modulation (where the frequency changes by a finite step) in the range from 1 to 3 kHz can be compressed as efficiently as a signal with a continuous frequency modulation when the frequency difference between components of the discrete-modulated signal is not greater than 100 Hz.