Using Powerful, Low-Frequency Radio Waves from Lightning to Diagnose the D-region Ionosphere

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This project will study the D-region electron density, at altitudes less than 95 km, using 3-300 kHz lightning radio emissions as a probe. In particular, new techniques will be applied to analysis of lightning radio emissions known as Narrow Bipolar Events in order to provide ionosonde-like retrievals of electron density profiles as well as information on the vertical and horizontal structure of D-region perturbations due to solar flares, particle precipitation, and thunderstorms. The primary research tasks are to develop an improved full wave propagation model which will provide more detailed ionospheric parameter extraction; to apply this technique to archived events to establish baseline D region ionospheric variability under a variety of conditions; and to apply to the results to open questions regarding radiation belt dynamics and lightning-ionosphere interactions. The theoretical electromagnetic model will be tested against observations of the propagation of lightning-generated radio waves detected simultaneously by multiple wide-band receivers at varying locations. Application of the model will enable inference of the D-region's horizontally-localized, instantaneous electron density profile in the vertical direction. This will be studied under a variety of geophysical conditions as well as the time variations caused by external influences such as magnetospheric and interplanetary disturbances, solar flares, and lightning itself. The tasks to be performed include: 1) Development of improved ionospheric radio-sounding technique using 3-300 kHz radiation from "Narrow Bipolar Event" lightning discharges; 2) Study of the vertical structure of D-region electron density profile in quiet, undisturbed conditions, using the improved sounding technique; 3) Study of vertical and horizontal structure of D-region perturbations due to solar flare activity, magnetospheric energetic particle precipitation and electron heating by the electrostatic fields of nearby thunderstorms and by electron heating by the radiated electromagnetic pulse of lightning strokes. The databases to be used includes the World Wide Lightning Location Network (WWLLN) and the Los Alamos Sferic Array. A graduate student will participate in the project.