Figure 3. Time series of count rates of 3 cm thick and 1 m2 area upper plastic scintillator of STAN3 array (energy threshold 2 MeV, a) and of NaI spectrometer with energy threshold 4 MeV (b). By black curve, we show disturbances of the near-surface electric field during long lasting flux enhancement.
As we can see In Fig. 3 the time series of particle detectors with an energy threshold above 2 MeV do not show any flux enhancement, thus, proving that the enhancement was originated only by isotope radiation, no electron acceleration in the atmosphere above detectors took place.
In Fig.4 we demonstrate the monthly distribution of TGE events originated by the RREA process in the atmosphere above detectors. The energy threshold of the used detector is above 4 MeV; in this way we exclude flux enhancement events originated by the isotope radiation only. As we can see in Figure no RREA occurred in 2017-2020 in the Winter months. Also, as we can see in the Figure in last 2 years the number of TGEs in April-May months abruptly diminished and total number of TGEs reduced ≈3 times in 2019-2020 compering with 2017 (the typic year for the TGE abundance in the previous 8 years).