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29 August 2003

Probing the Ionosphere Using Radios and Software

by Joseph DiVerdi, Ph.D., M.B.A.
XTR Systems, LLC

What follows is a PowerPoint file of the presentation given at the Second Annual Citizen Science Conference, in Pasadena, California, July 2003.

Very Low Frequency radio waves detected by earth-bound transmitters and receivers can be used to probe the ionosphere and detect energetic, extra-terrestrial events, such as solar flares and even Gamma Ray Bursts (GRBs). The transmitter and receiver are located sufficiently far apart to permit only "over-the-horizon" communication where the radio waves are reflected and refracted by the ionosphere, hence revealing its structure.

Transmitters are provided by the major Navies of the world which take advantage of the unique propagation features of the VLF radio waves to communicate with submarines operating at depth. Receivers, based on analog circuitry and capable of monitoring a single frequency, are commonly set up by amateurs and variously forwarded to the AAVSO-SID group for compilation.

The Northern Colorado Sudden Ionospheric Disturbance Observatory (NCSIDO) was created to continuously monitor the ionospheric structure and dynamics by monitoring multiple radio transmissions using Software Defined Radio (SDR). SDR is a class of techniques which replace many of traditional analog functions with digital and software processing components. The VLF range (3-30kHz) is especially convenient for the application of these techniques.

Click here to download the PowerPoint version of this presentation (5MB).