Broadband Integrated Remote Sensing of the D-region Ionosphere

The radio spectrum across the Extremely Low Frequency (ELF) to Very Low
Frequency (VLF) ranges defined as 1 Hz - 30 kHz is rich in signal sources historically used in remote sensing of the D-region ionosphere (60 - 90 km). Radio waves in this band have the property of propagating large distances with low attenuation, where ionospheric information is contained in the path-integrated measurements taken using a VLF receiver. Previous D-region remote sensing techniques have harnessed data received from isolated signal sources, which primarily include VLF MSK modulated transmitters operated by the Navy and lightning-generated radio emissions (sferics). Measurements of these sources have established techniques for producing D-region electron density profiles and have been shown to respond to sudden ionospheric disturbances due to space weather events. As signal sources overlap spectrally and temporally in data, it is often difficult to make a clean measurement of the specified signal of opportunity. We propose an integrated broadband remote sensing technique which aims to re-frame the signal processing problem as an optimization problem to concurrently analyze signal sources for the purposes of ionospheric remote sensing.