Flashes in the Middle and Upper Atmosphere Initiated by the Lightning Discharges: Recent Results and Future Optical and Spectral Observation Methods

Recent years yielded important experimental results in the field of studying the middle- and the upper-atmospheric discharges initiated by the lightning strokes. These results have been obtained using the most widespread measurement method related to the high-speed high-sensitivity visibleband cameras and the spectroscopy, which is the most rapidly developing method of observation of the upper-atmospheric flashes. Both methods are used during the ground-based, as well as the balloon- and satellite-borne observations. The above-mentioned methods are reviewed in this paper.