This grant continues research of the launching and propagation of primarily ELF waves, or "slow tails" associated with tropospheric lightning. The larger events are frequently accompanied by mesospheric optical emissions known as "red sprites" and/or "airglow events." The new equipment proposed will make more precise measurements to enable much more definitive science. Digital recording and subsequent digital filtering will eliminate the waveform distortion inherent in analog systems. The PI will conduct measurements from two different locations, enabling the evaluation of propagation independently of uncertain ionospheric models, facilitating extrapolation to the source. Finally, the PI will look into the feasibility of building a "sprite mapper," in conjunction with "lightning locator" data.