HR: 1330h
AN: AE42A-0797    [PDF]
TI: Measurement of Externally Driven D Region Ionospheric Variability
AU: * Cheng, Z
EM: zc@ee.duke.edu
AF: Duke University, 130 Hudson Hall Duke University, Durham, NC 27708 United States
AU: Cummer, S A
EM: cummer@ee.duke.edu
AF: Duke University, 130 Hudson Hall Duke University, Durham, NC 27708 United States
AB: Very low frequency (VLF) electromagnetic pulses launched from lightning, which are called sferics, are almost entirely reflected by the ionosphere below 100 km altitude and thus contain information about the D region ionosphere. In this work we examine the effects of three different external sources on the D region ionosphere. The first is lightning itself. Powerful electromagnetic pulses radiated from lightning discharges can cause direct heating and ionization of the lower ionosphere. Using VLF energy radiated from lightning that occurred before and after a big lightning discharge, we can measure D region ionosphere disturbance caused by big lightning flash. Our results will be compared to theoretical predictions (e.g. Taranenko et al., GRL, 1993). With the same measurement technique, we also measure the D region ionosphere variability due to solar flares such as X-class/M-class flares and relativistic electron precipitation. The daytime ionospheric change produced by big solar flares is clear. Using SAMPEX energetic particle data we also find clear nighttime ionospheric changes when significant particle precipitation is present.
DE: 2435 Ionospheric disturbances
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2003 Fall Meeting