ИСТИНА

Particle acceleration in a short time scales is still an important question both in magnetosphere physics and in atmospheric and thunderstorm physics. In the first case, it is connected with the wave-particle interaction and the possibility of different plasma waves to create short pulses of relativistic and sub-relativistic electrons. In the second case, it is the problem of formation of discharges and beams of relativistic electrons in electric fields, significantly below breakdown threshold. In our work we use high-temporal-resolution imaging photometers and spectrometers to measure the fluorescence emission of the atmosphere when particle beams pass through. Such measurements allow us to study the spatiotemporal structure of the beams and their energy spectrum. The report presents two examples of such observations: recently discovered optical microbursts (OMBs) in the auroral zone during measurements at Kola peninsula (PAIPS projects) and the fine temporal structure of radiation during thunderstorms at the Aragats Observatory. OMBs optical spectrum measurements have shown that the energy of the precipitating particles responsible for the occurrence of OMBs is more than 100 keV, which is significantly higher than the energy of auroral electrons. Studies of wave activity during these events indicate connection with chorus waves, but the statistical distribution of the MLT is if favour of EMIC waves. Measurements of the near-UV emission during thunderstorm and comparison with electric field, gamma-ray and particle fluxes Aragats observatory demonstrate increase in trigger frequency, presence of short flashes with high-speed movement during and immediately before the return stroke. These flashes may be associated with the fluorescent emission of terrestrial gamma-ray flashes (TGFs) and fine temporal structure of thunderstorm ground enhancements (TGEs) discovered earlier at Aragats. Data analyses of both experiments is in progress. This research was founded by Russian Science Foundation grant number 22-62-00010.