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).