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The influence of thunderstorms' atmospheric electric fields (AEF) on secondary cosmic rays (CR) detected at high altitude was studied. Using data obtained during the period October 2019 to March 2020 by the Solar Neutron Telescope (SNT) and a Boltek EFM-100 AEF monitor installed in the Sierra Negra Cosmic Ray Observatory (SN-CRO) located at 4580 m a.s.l. in Mexico. With measurements from the EFM-100, 15 thunderstorms were identified during the established period. Based on the general theory of AEF effects on CR, due to acceleration and deceleration of secondary charged CR particles by AEF, proposed by Dorman (2004), we calculated, as a first approximation, the effect on the total charged component (1.15%–3.47%) at the observation level of the SN-CRO. Simulations of air showers in the presence of a simplified electric field were performed with the CORSIKA code and EXPACS software to complement the calculations. When thunderstorms occurred above SN-CRO, significant fluctuations in the average counting rate of three SNT channels were observed and were consistent with the calculated intensity variations. [ABSTRACT FROM AUTHOR]

• Solar neutron flux. • Simulations. • Olar neutron telescope. We performed simulations of the solar neutron (n s) flux in the Earth's atmosphere associated with three significant flares (X17 of September 07, 2005, X1.3 of September 07, 2017 and M2.9 of September 08, 2017). The input of the simulations was calculated on the basis of n s signals detected at ground level by the Solar Neutron Telescope of Sierra Negra (SNT-SN), in Mexico, and by the FIB scintillator of the Space Environment Data Acquisition-Attached Payload on board of the International Space Station. Since n s can produce Extensive Air Showers (EAS) in the Earth's atmosphere, we used the CORSIKA code and FLUKA subroutines to simulate the particle fluxes associated with the X17, X1.3 and M2.9 flares. We studied the average longitudinal variations of particle flux and energy loss through the atmosphere to estimate the n s flux impinging on the SNT-SN. The results of the simulated interactions and multiplicities of the particles, as a function of their energy, showed that 11–13% of the n s , released by the X17 flare, could overcome the atmospheric attenuation and propagate from the top of the atmosphere to the SNT-SN (4580 m a.s.l.) without producing EAS. On the other hand, n s associated with the X1.3 and M2.9 flares were lost due to atmospheric attenuation and the production of new particles; therefore, they were not detected at ground level by the SNT- SN. The characterization of these events allowed to develop an automatic tool for the analysis of n s emissions associated with solar flares. [ABSTRACT FROM AUTHOR]