Scientific motivation
BACKGROUND
New emerging field of high-energy atmospheric physics (HEAP) is still lacking firmly established concepts and theories. The relationship of lightning and elementary particle fluxes in the thunderclouds is not fully understood to date. HEAP presently includes 2 main physical phenomena: Terrestrial Gamma Flashes (TGFs) - brief burst of gamma radiation (sometimes also electrons and positrons) registered by the orbiting gamma ray observatories in the space and Thunderstorm ground enhancements (TGEs) -the prolonged particle fluxes registered on the ground level|. Both TGFs and TGEs are related to the thunderstorms and lightning flashes: TGEs - by directly detecting electric field and lightning occurrences above the detector site; TGFs by making rather complicated synchronization with worldwide lightning detecting networks. The central engine initiated TGE is believed to be the Relativistic Runaway Electron avalanches (RREA) accelerated seed electrons from ambient population of cosmic rays (CR) in the large-scale thundercloud electric field up to 40-50 MeV. Observation of numerous TGEs by the Japanese, Russian, Armenian, Chines, Slovakian groups prove that RREA is a robust and realistic mechanism for electron acceleration and multiplication leaving no doubts about correctness of the RREA model for the TGE initiation. Models using CERN origin GEANT4 code support in situ measurements of electron and gamma ray energy spectra at Aragats. Another model of the gamma glow initiation was used for explaining gamma ray detections by TERA array in Florida. The main idea of the model is thermal electron acceleration in the streamer tips up to energies of ∼65 keV; thereafter these electrons runaway and accelerate further by the extreme electric field in the streamer zone in vicinity of negative lightning leader. This 2-stage model includes development of very strong electric fields in very short times. Correspondingly, the model includes compatible theories and models with several parameters which values are very difficult to measure or estimate (for instance the electric field of 260 kV/cm in the lightning leader tip, or- field strength and elongation in the streamer zone where runaway electrons suppose to reach MeV energies). Thus, many questions about thundercloud electrification and discharge mechanisms, lightning initiation, propagation and attachment processes, the global electrical circuit, and transient luminous events do not have a complete and common accepted explanation yet. One of the most important problems “do lightning flashes produce relativistic particles or not?” is still open. TEPA meeting is great opportunity for scientist to meet, discuss, invent new ideas and make new bridges for collaborative works.
STRUCTURE OF THE SYMPOSIUM:
We anticipate the following sessions:
- Models of high-energy emissions in thunderclouds;
- Multivariate observations of thunderstorms from the Earth’s surface and from space;
- Particle fluxes and lightnings – any causal relations?
- Research of the Thunderstorm ground enhancements (TGEs);
- Research of the Terrestrial gamma-ray flashes (TGF);
- Extensive air showers, lightning and RB/RREA process;
- Atmospheric High-energy phenomena observations by space-born facilities
- Instrumentation
We plan also discussions on the most intriguing problems of high-energy physics in the atmosphere and on possible directions for the advancement in the collaborative studies.
Topics to be covered during oral and poster sessions:
▪ Research of the Thunderstorm ground enhancements (TGEs), measurements of electrons, gamma rays and neutrons by networks of particle detectors located on Earth’s surface;
▪ Research of the Terrestrial gamma-ray flashes (TGFs) observed by the orbiting gamma-ray observatories;
▪ Radio emissions produced by atmospheric discharges and particle fluxes;
▪ Lightning initiation and its relation to particle fluxes originated in thundercloud;
▪ Neutron production during thunderstorms;
▪ Ultraviolet and infrared emissions during thunderstorms;
▪ Monitoring of thunderclouds and particle emission from orbit;
▪ Monitoring of the thunderstorms by high speed cameras e;
▪ Methods of the remote sensing of the thundercloud structure and electric field;
▪ X-ray emissions from the lightning;
▪ Abrupt termination of the particle flux by the lightning flash;
▪ Precise electronics for the high-energy atmospheric research;
▪ Relations to the climate and space weather issues;
▪ Possibility of joint observations by space-born and ground-based facilities.
▪ The global electrical circuit.
