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This study investigates the modulation of particle fluxes at the Earths surface influenced by the intensity and orientation of the Interplanetary magnetic field (IMF) carried by the Coronal Mass Ejecta (ICME). We examine how IMF and its Bz component, opposing the magnetosphere, significantly enhance geomagnetic activity through magnetic reconnection. This reconnection facilitates increased penetration of solar wind particles into the magnetosphere, thus amplifying the fluxes registered by terrestrial particle detectors and enhancing particle fluxes through reduced cutoff rigidity (magnetospheric effect, ME). Conversely, the orientation of the Bz component is less crucial for a Forbush decrease (FD); instead, the strength of the ejecta's scalar magnetic field (B) predominates, potentially triggering a significant FD. The study explores how magnetic field variations influence the flux of neutrons and muons, effectively modifying the observed rates of cosmic ray influx. Comprehensive data from the WIND magnetometer and Aragats spectrometers underline the direct relationship between ICME magnetic configurations and variations in ground-level particle fluxes. Moreover, we discover that the energy spectra of additional particles during ME are limited to 10 MeV due to the low energy of solar protons entering the terrestrial atmosphere. In contrast, the energy spectra of the missing FD particles can extend up to 100 MeV, demonstrating that magnetic traps and cradles formed by interactions between ejecta and Earth's magnetic fields can also deflect medium-energy solar protons. These insights advance our understanding of geomagnetic modulation of particle fluxes and bolster predictive models of space weather impacts on particle detection technologies.

In 2023, a series of intense Thunderstorm Ground Enhancements (TGEs) were recorded on Mount Aragats in Armenia, with five events exceeding the fair-weather cosmic ray flux by more than 100 percent. This study comprehensively analyzes these TGEs, investigating the atmospheric conditions and electric fields contributing to their occurrence. Key insights include discovering relationships between TGEs and atmospheric electric fields, recovering electron and gamma-ray energy spectra, and the impact of nearby lightning activity. The findings offer a deeper understanding of TGEs' role in atmospheric physics and its synergy with high energy astrophysics.

During the multiyear monitoring of particle fluxes and near-surface electric field (NSEF) on the Aragats research station, no runway relativistic electron avalanches have been observed in the January-February months. The large peaks and energies of TGE particles originating from the electron-gamma avalanches in the thundercloud are observed in the Spring-Autumn months when the electric field inside the cloud often exceeds the runaway threshold strength. On February 7, 2023, suddenly, all particle detectors registered 3 TGEs within 10 hours without any unusual local weather conditions. We consider these TGEs as indirect evidence of the influence of strong earthquakes on the previous day on the ionosphere and via the ionosphere on the structure and strength of the intracloud electric field above Aragats mountain. Recovered energy spectra of TGE electrons and gamma rays prove nearly one hour the strength of the electric field above Aragats at the heights 3300-5300 m comprises 2.1 kV/cm.

On November 3-4 2021, an interplanetary coronal mass injection (ICME) hits the magnetosphere, sparking a strong G3-class geomagnetic storm and auroras as far south as California and New Mexico. All detectors of the SEVAN network registered a Forbush decrease (FD) of 5-10 percentdeep in 1 minute time series of count rates. We present the results of a comparison of Fd registered on mountain altitudes on Aragats (Armenia), Lomnicky Stit (Slovakia), Musala (Bulgaria), and at sea level DESY (Hamburg, Germany), and in Mileshovka, Czechia. We present as well purity and barometric coefficients of different coincidences of SEVAN detector layers on Aragats. We demonstrate disturbances of the near-surface electric (NSEF) and geomagnetic fields at the arrival of the ICME on Earth.

Proceeding from a stormy day of 22 September 2022, when 7 thunderstorm ground enhancements occurred (TGEs, 3 of them very large), we perform an analysis of the most important conditions, on which depend the origination of the large particle fluxes in the thunderous atmosphere. Among these conditions are the near-surface electric field (NSEF), graupel fall, and lightning activity. We estimate the intensity of the largest particle flux of 1,25 mln gamma rays hitting each square meter of surface on Aragats with energy spectra extended up to 70 MeV. Only one TGE from 7 meets the conditions to recover the electron energy spectrum; the fraction of electrons with energies above 10 MeV relative to the gamma ray flux reaches 45%. By carefully examining the graupel fall, we demonstrate that the lower dipole, which accelerates electrons, is formed by the main negative and lower positively charged regions. The lower dipole decays with a graupel fall that coincides with TGE terminations (usually by a lightning flash).

We present a survey of more than half a thousand thunderstorm ground enhancements, fluxes of electrons, and gamma rays associated with thunderstorms registered from 2008 to 2022 at Aragats space environmental center. We analyze correlations between various measured parameters characterizing TGEs measured on Aragats. Two special cases of TGE events are considered: one, terminated by nearby lightning flashes, and another one with a sufficiently large ratio of electrons to gamma rays. On the basis of the analysis, we summarize the most important results obtained during 12 years of TGE study, which include: We show the operation of the electron accelerators in the thunderous atmosphere by directly measuring the electron flux during thunderstorms; Quite frequently, TGEs occur prior to lightning flashes and are terminated by them. The energy spectra of avalanche electrons observed on Aragats indicate that the strong electric field region can extend very low above the ground covering a large area on the ground. TGEs originated from multiple relativistic runaway electron avalanches (RREAs) starting with seed electrons from the ambient population of cosmic rays, which enter an extended region of the electric field with strength exceeding the critical value.

In the present report, we describe the NaI particle detector network and present the first results of the experiment demonstrating that the particle fluxes from the atmospheric electron accelerators can cover large areas on the earth surface., Comment: 16 pages 12 figures

We present and discuss Transient Luminous Events in the lower atmosphere, observed during large disturbances of the near-surface electric fields (NSEF) and coinciding with large enhancements of the particle fluxes.

We present the facilities of the Aragats Space Environmental Center in Armenia used during multi-year observations of the thunderstorm ground enhancements (TGEs) and corresponding environmental parameters. We analyze the characteristics of the scintillation detectors, operated on Aragats, and describe the coordinated detection of TGEs by the network of scintillation detectors, field meters, and environmental parameters. By using a fast synchronized data acquisition system we reveal correlations of the multivariate data on time scales from second to nanosecond which allow us to gain insight into the TGE and lightning origin and their interrelations.

Aragats solar neutron telescope (ASNT) is a unique instrument allowing to measure the energy spectra of electrons accelerated and multiplied in the strong electric fields of the atmosphere. We describe the instrument setup, its operation condition, software, and hardware triggers. We present energy spectra of a very large thunderstorm ground enhancement (TGE) event observed on 6 October 2021.