Identification of Whistler Waves in VLF Spectra

Left: Cartoon depicting whistler wave propagation. Right: Noisy spectrogram with whistler events observed at Marion Island in 2012.

Believe it or not, lightning is harnessed to do space physics. When lightning strikes a powerful electromagnetic pulse (EMP) is created at cloud level, resulting in some of the energy to escape the atmosphere, travelling along the Earth's magnetic field lines in the form of "whistler waves". These waves propagate along field lines into near earth space, and back to the ground in the opposite hemisphere where they are observed in the very low frequency (VLF) band by antennas installed in exotic places such as Antarctica and Marion Island. By monitoring the observed change in frequency of the incoming wave we can estimate particle density on the field line, which is important for studying energetic particle dynamics in the magnetosphere. A critical first step in these studies is the efficient identification and characterisation of whistler wave events.

This problem is neatly distilled to: "Find the curvy lines in the spectrogram!". Image processing and machine learning techniques will be used to find known whistlers in a large set of spectrograms. The performance of this model will be judged against the current state of the art analytic models.