ИСТИНА

The Vernov satellite was launched in 2014 into a polar solar-synchronous orbit with small eccentricity 640x830 km and period about 98 min. Such orbit provides favorable conditions for the Atmosphere study at different latitudes including Equatorial and Polar Regions. The wide band observations of the Atmosphere from radio to gamma rays as well as detection of relativistic electrons and electromagnetic waves in the near-Earth space were realized by RELEC payload in this experiment. The main instrument for TGF observation is DRGE gamma-ray spectrometer with four detectors directed to atmosphere providing measurements in 10-3000 keV energy range with time resolution ~15 mcs. Total area of DRGE detectors is ~500 cm2. The data were recorded both in monitoring and gamma by gamma modes. Terrestrial Gamma Flashes (TGF) were observed during the Vernov mission from July, 8 to December, 14, 2014. Events with 10-40 gammas in a burst with duration <1ms were detected. The TGF candidate database includes dozens of events among which a few ones were detected in Polar Regions far away from Thunderstorms. The duration of polar events is about few milliseconds being some longer than the duration of equatorial ones. There is no direct indication that those flashes were accompanied by radio pulses in low frequency (~0.1 – 4104 Hz) and radio frequency (0.05-15 MHz) bands as well as by lightning from WWLN. The possible connection of these events with electron precipitation is under discussion. Similar 10-3000 keV gamma-ray detectors are used in BDRG instrument on-board Lomonosov satellite launched to the polar ~500 km high orbit on 28.04.2016. The instrument was designed for cosmic GRB study but its characteristics allow one to provide the TGF search using fast on-board trigger (t=10ms) as well as the analysis of non-triggered data recorded in gamma-by-gamma mode. The first results of TGF search by BDRG/Lomonosov are reported.