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B. Sargsyan

Publications and source records attributed to B. Sargsyan.

17 recordsLinked to original sources
arXiv2026

Direct Observation of Wilsonian Electrons in Thunderstorms

We analyze electron rich Thunderstorm Ground Enhancements (TGEs) detected at Aragats using the SEVAN Light spectrometer, which can separate charged and neutral particles and reconstruct their energy spectra. The events exhibit large electron fluxes, with reconstructed energies extending to 45 MeV. Simultaneous meteorological observations reveal that all events occurred within a remarkably narrow atmospheric regime characterized by exceptionally low cloud-base heights, temperatures near 0°C, strong electric-field disturbances, and lightning. Comparisons with the complete Aragats TGE archive demonstrate that the direct detection of runaway electrons becomes possible only when the active acceleration region approaches within several tens of meters of detector altitude, allowing electrons to survive atmospheric attenuation. These results provide an experimental explanation for the century long rarity of observations of Wilsonian electrons. The findings establish the atmospheric conditions required for direct observation of runaway electrons and contribute to the understanding of particle acceleration in natural electric fields.

physics.ao-ph↗
arXiv2026

Positron acceleration in thunderstorms

Thunderstorm Ground Enhancements (TGEs) are known manifestations of relativistic runaway electron avalanches (RREAs) developing inside thunderclouds. However, the role of positrons in TGEs and their relationship to thundercloud charge structure remain poorly understood. We report time resolved observations of intense positron fluxes detected at the Aragats Observatory on 16 17 May 2026 during strong thunderstorms. Two of the three events were characterized by a positive near surface electric field (NSEF), graupel precipitation, a low cloud base, and low-to-moderate enhancement of gamma ray and electron fluxes measured by SEVAN and STAND3 detectors. The third event is a classical electron TGE considered for comparative purposes. All events show moderate to strong enhancement of the 511 keV annihilation line, along with enhanced radon progeny gamma ray lines. We observe a temporal separation between the electron and gamma ray TGE peak and the positron flux maximum. To explain these observations, we introduce a dual dipole electrodynamic model. The large scale electron dipole comprises the main negative thundercloud layer and its broad positive mirror charge induced at the Earths surface, producing ordinary TGEs. Simultaneously, a localized positron dipole forms from the LPCR, with its negative mirror charge directly beneath the LPCR footprint. This lower dipole accelerates positrons downward while decelerating electrons entering the same region. These results establish positron TGEs as a new subclass of atmospheric high energy phenomena and provide direct evidence of localized positron acceleration in the lower atmosphere.

physics.ao-ph↗
arXiv2026

Continued activity of the 25th cycle: largest in 20 years. Ground-level enhancement and Forbush decrease

After a very calm 24th solar activity cycle, the 25th cycle has already seen several interesting events. A Ground Level Enhancement GLE77 was observed on 11 November 2025 following an X5.1 class solar flare. A strong Forbush decrease occurred on 19 and 20 January 2026 during one of the most intense geomagnetic storms of Solar Cycle 25. Events were recorded coherently by the global neutron monitor network and by SEVAN detectors at multiple altitudes. Using spectrometric capabilities, we reconstruct energy spectra of missing neutrons and muons during the FD and compare them with corresponding spectra measured during GLE77. The analysis demonstrates that FD and GLE signatures are intrinsically asymmetric. FDs selectively suppress the preexisting galactic cosmic ray population, whereas GLEs introduce an additional, harder particle component. Neutron and muon channels exhibit markedly different spectral behavior, particularly at higher deposited energies, reflecting their sensitivity to different primary energy ranges. These results show that combined NM and SEVAN observations provide robust, complementary diagnostics of rigidity dependent cosmic ray modulation during extreme heliospheric disturbances.

physics.ao-ph↗
arXiv2025

High-Energy Atmospheric Radiation: From Thunderstorm Ground Enhancements to Terrestrial Gamma-Ray Flashes

This work presents a unified conceptual and observational framework that reinterprets these radiation bursts as manifestations of the same runaway processes happening at different atmospheric depths (Dual-stage model, DSM). We review recent results from satellite (ASIM), aircraft (ALOFT), balloon (HELEN), and ground-based (SEVAN and KANAZAWA) experiments to demonstrate the advantages of this integrated approach. This study addresses key contradictions in the field, introduces new classification criteria based on physics rather than detector location, and enhances our understanding of particle acceleration in thunderstorms.

physics.space-ph↗
arXiv2025

Solar neutron and muon detection on November 11, 2025: First simultaneous recovery of energy spectra

Ground Level Enhancement (GLE) events provide rare opportunities to study high-energy solar particle acceleration through direct detection of secondary radiation at ground level. On November 11, 2025, the Aragats Solar Neutron Telescope (ASNT) recorded a statistically significant increase in high-energy neutron and muon fluxes associated with an X5.1 flare and the subsequent Solar Energetic Proton (SEP) event. The event displayed a unique dual-peak profile: an initial hard component at 10 28 UT, followed by a softer yet still energetic peak at 10 45 UT. For the first time, we report simultaneous energy spectra of atmospheric neutrons and muons measured in the 10 600 MeV range at Aragats. Broken-power-law fits reveal a clear temporal evolution of acceleration conditions, evidenced by spectral indices declining with energy. These findings highlight the unique capabilities of the ASNT as an instrument for studying extreme solar particle acceleration.

astro-ph.SR↗
arXiv2025

The largest Forbush decrease in 20 years: Preliminary analysis of SEVAN network observations

We present a preliminary analysis of the largest Forbush Decrease (FD) observed in solar cycle 25 using SEVAN network data. Triggered by consecutive Earth-directed CMEs on May 30 and 31, 2025, this event produced two distinct FD minima and a prolonged recovery, with significant anisotropies in cosmic ray response across the network. The timing of interplanetary shock arrivals was confirmed by SSC signatures at 05:22 UTC on June 1 and 10:19 UTC on June 2, marking the onset of each FD phase. The depth and temporal structure of the FD varied across SEVAN detectors, providing insights into the complex heliospheric and magnetospheric dynamics during this multi-CME event.

astro-ph.SR↗
arXiv2025

Wind-induced Natural Gamma Radiation

During the extreme winter storms of 2024-2025 at Aragats, natural gamma radiation (NGR) increased by more than 1000%, with fluence reaching 2*10^7 gammas/cm^2 over 10 hours and a corresponding dose of 3.26 mSv, 120 times higher than normal background radiation for the same period. This unprecedented radiation surge was detected during dry, electrified snowstorms, exceeding levels explainable by known atmospheric mechanisms, necessitating a significant reassessment of gamma-ray sources in winter storm conditions. These results suggest similar radiation surges may occur in high-altitude and polar regions (Arctic and Antarctic), where strong winds and prolonged snowstorms are common. Understanding radiation surge conditions is essential for refining atmospheric models, improving radiation monitoring, and assessing environmental and climatic impacts in extreme weather conditions.

physics.ao-ph↗
arXiv2024

Influence of Interplanetary Coronal Mass Ejec5ons on Terrestrial Par5cle Fluxes Through Magnetosphere Disturbances

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.

physics.space-ph↗
arXiv2024

Extreme thunderstorm ground enhancements registered on Aragats in 2023

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.

physics.ao-ph↗
arXiv2023

Very unusual operation of the electron accelerator above Aragats mountain in Armenia a day after the earthquake in Turkey and Syria

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.

physics.ao-ph↗
arXiv2022

Forbush decrease observed by SEVAN particle detector network on November 4, 2021

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.

physics.space-ph↗
arXiv2022

Genesis of thunderstorm ground enhancements

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).

physics.ao-ph↗
arXiv2022

Thunderstorm Ground Enhancements: Multivariate analysis of 12 years of observations

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.

physics.ao-ph↗
arXiv2022

Multi-messenger observations of thunderstorm-related bursts of cosmic rays

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.

physics.ins-det↗
arXiv2022

Measurements of energy spectra of relativistic electrons and gamma-rays avalanches developed in the thunderous atmosphere with Aragats Solar Neutron Telescope

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.

physics.ao-ph↗