Superior VLF Remote Sensing of the Ionosphere Using Stokes Parameters

Very low frequency (VLF, 3-30 kHz) radio waves can propagate large distances around the Earth within the Earth-ionosphere waveguide with relatively low attenuation.  As a result, careful measurements of the amplitude, phase, and polarization of subionospherically-propagating VLF waves can be used to remote-sense the D-region ionosphere over large swaths of the Earth.  In this paper, we present a new signal processing method for calculating the amplitude, phase, and polarization of subionospherically-propagating VLF waves.  The method allows for impulsive sferic rejection as well as local interference rejection, and the integration method mitigates (to some degree) the impact of receiver system noise on the measurement.  We apply the new method to a variety of natural VLF events, such as early/fast VLF events and lightning-induced electron precipitation events, and we compare the performance of the method with the performance of other well-known VLF signal processing methods.