December 1, 2010, 12:00 pm - 1:00 pm

December 1, 2010, 12:00 pm - 1:00 pm

Global Quantification of Lighting-induced Electron Precipitation using VLF Remote Sensing

Ben Cotts (Stanford University)

High energy electrons are trapped by the Earth's magnetic field in what are known as the Van Allen Radiation Belts. Understanding and limiting the lifetime of these radiation belt electrons is a critical factor in predicting the failure rate of satellites as this radiation degrades the performance of on-board electronics. These high energy electrons can be removed from the radiation belts in a process called Lightning-induced Electron Precipitation (LEP) whereby gyro-resonant interactions with lightning-generated whistlers alter the pitch angle of trapped electrons such that they will be precipitated into the atmosphere. Quantification of this loss is accomplished by observing subionospherically propagating VLF signals with the path between the transmitter and receiver lying under the resulting ionospheric disturbance. Observations of LEP events at three locations show characteristics which systematically vary with both longitude and hemisphere. These observations are quantitatively interpreted with the use of a novel model of atmospheric backscatter which can be used to predict the characteristics of LEP events at any longitude and mid-latitude L-shell. By accounting for the asymmetry of Earth's magnetic field in backscatter calculations it is possible to link the total electron precipitation at conjugate points of the same field line and to estimate radiation belt electron loss rates due to lightning even in remote portions of the world where there are few VLF receivers and even fewer VLF transmitters (e.g., over much of Africa). Combining these results with previously calculated radiation belt electron loss rates due to lightning at a single longitude will provide a global estimation of radiation belt electron loss due to lightning.