VLF Imaging of Lightning-Induced Disturbances of the Lower Ionosphere

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The PI proposes an experimental investigation of lower ionosphere localized and transient disturbances, occurring with lightning discharges. These disturbances are remotely sensed by their effect on the phase and amplitude of very low frequency (VLF) signals propagating in the nearby Earth-ionosphere waveguide. This program is an outgrowth of previous VLF observation programs, and will establish an experiment configuration of measurements at multiple sites, constituting two arrays (east and west). These arrays provide high resolution measurement of disturbances, capturing a sufficient number of necessary events, and providing a database for holographic imaging of the disturbances' size. Ionospheric disturbances may be produced by lightning radiation and quasi-static fields directly interacting with the ionosphere, or by bursts of energetic electrons precipitated out of the radiation belts by whistler waves originating in lightning discharges. Both phenomena regularly occur; however, the PI must determine the spatial extent and distribution of these events to assess their global significance. He will transfer data from field sites over the Internet, making it available to the scientific community in near real-time. Finally, this program will provide important educational outreach, since field equipment will be deployed at high schools, where students and teachers will be encouraged to interact with Stanford University investigators.