Title:  Evaluating the role of lightning-induced electron precipitation towards radiation belt electron loss

Committee:

Dr. Morris Cohen, ECE, Chair, Advisor

Dr. Sven Simon, EAS

Dr. David Anderson, ECE

Dr. Andrew Peterson, ECE

Dr. Paul Steffes, ECE

Abstract: Lightning-induced electron precipitation (LEP) is one of the principle mechanisms for electrons to be drained from the radiation belts. An LEP event progressess with Very Low Frequency (VLF) radio wave propagation from lightning, trans-ionospheric propagation, and wave-particle gyroresonance interaction with energetic radiation belt electrons. Scattered electrons then precipitate onto the ionosphere, and this disturbance is detected of these events through VLF signals scattering off the disturbed ionosphere. This research attempts to quantify the role of LEP events, through several steps. First, we build a massive database of LEP events observed within the continental US (CONUS) by a network of VLF receivers. To do this, we employ the use of an Artificial Neural Network (ANN) classifier, in order to automatically detect LEP events from VLF signals. Second, we apply a model to estimate the total number of precipitating electrons, which we can then sum up over all LEP events to quantify lightning's contribution within CONUS. We draw on a cascading trio of models to construct of LEP events, including a ray tracing code for whistler wave propagation, a model of electron deposition into the ionosphere, and finally a model of VLF propagation. Finally, we examine data from the Van Allen Probes, both to investigate the correlation between electron distributions and the occurrence of LEP events, and to provide a reference for the total number of electrons available in the belts to be removed. We find that LEP events within CONUS appear to be capable of removing a substantial fraction (up to 0.1%-1%) of radiation belt electrons between 33 keV and 1000 kA.