On the initiation of lightning in thunderclouds

The relationship of lightning and elementary particle fluxes in the thunderclouds is not fully understood to date. Using the particle beams (the so-called Thunderstorm Ground Enhancements-TGEs) as a probe we investigate the characteristics of the interrelated atmospheric processes. The well-known effect of the TGE dynamics is the abrupt termination of the particle flux by the lightning flash. With new precise electronics, we can see that particle flux decline occurred simultaneously with the rearranging of the charge centers in the cloud. The analysis of the TGE energy spectra before and after the lightning demonstrates that the high-energy part of the TGE energy spectra disappeared just after lightning. The decline of particle flux coincides on millisecond time scale with first atmospheric discharges and we can conclude that Relativistic Runaway Electron Avalanches (RREA) in the thundercloud assist initiation of the negative cloud to ground lightning. Thus, RREA can provide enough ionization to play a significant role in the unleashing of the lightning flash

Analyzing atmospheric electric field by the European SEVAN network of particle detectors

Particle detectors of the European SEVAN network located on mountain heights in Aragats (Armenia), Lomnický štít (Slovakia) and Musala (Bulgaria) are well suited for the detection of thunderstorm ground enhancements (TGEs, enhanced fluxes of electrons, gamma rays, neutrons). The modulation of charged particles flux by the electric field of the thundercloud results in a sizable change in the count rate of detectors, which measure fluxes of electrons, gamma rays, and high energy muons in the near-vertical and near-horizontal directions. The relation between electric field strength and changes of particle flux count rates is nonlinear and depends on many unknown parameters of atmospheric electric field and meteorological conditions. Nonetheless, employing extreme TGEs as a manifestation of the strong electric field in the thundercloud and by measuring fluxes of three species of secondary cosmic rays (electrons, gamma rays, and muons) by SEVAN detectors located at altitudes of ≈ 3 km we study the extreme strength of the atmospheric electric field. With the simulation of particle traversal through the electric field with CORSIKA code (https://www.iap.kit.edu/corsika/index.php, last accessed April 21, 2021), we derive a maximum potential difference in the thunderous atmosphere to be ≈ 500 MV

MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

https://pos.sissa.it/395/815/pdfPublished versio

Thunderstorm Ground Enhancements Measured on Aragats and Progress of High-Energy Physics in the Atmosphere

High-energy physics in the atmosphere (HEPA) has undergone an intense reformation in the last decade. Correlated measurements of particle fluxes modulated by strong atmospheric electric fields, simultaneous measurements of the disturbances of the near-surface electric fields and lightning location, and registration of various meteorological parameters on the Earth have led to a better understanding of the complex processes in the terrestrial atmosphere. The cooperation of cosmic rays and atmospheric physics has led to the development of models for the origin of particle bursts recorded on the Earth’s surface, estimation of vertical and horizontal profiles of electric fields in the lower atmosphere, recovery of electron and gamma ray energy spectra, the muon deceleration effect, etc. The main goal of this review is to demonstrate how the measurements performed at the Aragats cosmic ray observatory led to new results in atmospheric physics. We monitored particle fluxes around the clock using synchronized networks of advanced sensors that recorded and stored multidimensional data in databases with open, fast, and reliable access. Visualization and statistical analysis of particle data from hundreds of measurement channels disclosed the structure and strength of the atmospheric electric fields and explained observed particle bursts. Consequent solving of direct and inverse problems of cosmic rays revealed the modulation effects that the atmospheric electric field has on cosmic ray fluxes

Monitoring of the atmospheric electric field and cosmic-ray flux for the interpretation of results in high-energy astroparticle physics experiments

Atmospheric electric fields influence experiments using the atmosphere as a detector for very weak fluxes of highest-energy gamma rays and protons/nuclei coming from galactic and extragalactic sources. Multiplication of electrons and gamma rays in strong atmospheric electric fields change particle numbers and energy spectra of the secondary shower particles and consequently influence the reconstructed properties of the primary particles. Here, we present a MC study using the CORSIKA package to explore and quantify these effects

Transient Luminous Events in the Lower Part of the Atmosphere Originated in the Peripheral Regions of a Thunderstorm

We present and discuss transient luminous events (TLEs) in the lower atmosphere, observed during large disturbances of the near-surface electric fields (NSEF) and coinciding with large enhancements of the particle fluxes (thunderstorm ground enhancements—TGEs). Despite large distances from the strongest electric field region, the maximum energy of TGE particles on 22 and 25 May 2018 reaches ≈40 MeV. Thus, the accelerating electric field reaches ≈2.0 keV/cm far from the zone of the strong lightning activity on the periphery of the storm. Light glows appearing simultaneously in the skies may be due to the local charge rearrangement generating a small illuminating discharge without initiating the lightning flash. This type of charge rearrangement does not lower the potential difference in the cloud, allowing the electron accelerator to operate and send particle fluxes in the direction of the earth’s surface

Techniques for characterizing weak transients in cosmic ray records, as measured by neutron monitor networks

International audienceThe analysis of weak variations in the energetic particle flux, as detected by neutron or muon monitors, can often be considerably improved by analysing data from monitor networks and thereby exploiting the spatial coherence of the flux. We present a statistical framework for carrying out such an analysis and discuss its physical interpretation. Two other applications are also presented: filling data gaps and removing trends. This study focuses on the method and its various uses

Transient Luminous Events in the Lower Part of the Atmosphere Originated in the Peripheral Regions of a Thunderstorm

We present and discuss transient luminous events (TLEs) in the lower atmosphere, observed during large disturbances of the near-surface electric fields (NSEF) and coinciding with large enhancements of the particle fluxes (thunderstorm ground enhancements—TGEs). Despite large distances from the strongest electric field region, the maximum energy of TGE particles on 22 and 25 May 2018 reaches ≈40 MeV. Thus, the accelerating electric field reaches ≈2.0 keV/cm far from the zone of the strong lightning activity on the periphery of the storm. Light glows appearing simultaneously in the skies may be due to the local charge rearrangement generating a small illuminating discharge without initiating the lightning flash. This type of charge rearrangement does not lower the potential difference in the cloud, allowing the electron accelerator to operate and send particle fluxes in the direction of the earth’s surface