Scientific Motivation

BACKGROUND:

New emerging field of high-energy atmospheric physics (HEAP) is enriched recently by important observations of particle fluxes on Earth’s surface, in troposphere and in the space. HEAP presently includes 3 main types of measurements: Terrestrial Gamma Ray Flashes (TGFs) - brief burst of gamma radiation (sometimes also electrons and positrons) registered by the orbiting gamma ray observatories in the space; TGEs - prolonged electron and gamma ray fluxes (also neutrons) registered on the earth’s surface;| and gamma glows - gamma ray bursts observed in the thunderclouds by facilities on balloons and aircraft.

The central engine initiating the TGE is believed to be the Relativistic Runaway Electron avalanches (RREA), that accelerates seed electrons from an ambient population of cosmic rays (CR) in the large-scale thundercloud electric fields. Observation of numerous TGEs by Japanese, Russian, Armenian, Chines, and Slovakian groups prove that RREA is a robust and realistic mechanism for electron acceleration and multiplication leaving no doubts about the correctness of the RREA model for the TGE initiation. The precisely recovered particle energy spectra gives new glues for testing models of electron acceleration in atmosphere, as well as for scrutinizing the structure of the electric fields in thunderclouds. Models using GEANT4 and CORSIKA codes support in situ measurements of electron and gamma ray energy spectra at Aragats. Numerous observations of TGEs made on Aragats during last 11 years can be widely used for the validation of models aimed to explain TGF phenomena.

The relationship of lightning and elementary particle fluxes in the thunderclouds was established on microsecond timescales. The particles flux data, well synchronized with the information on atmospheric discharges give valuable information on the structure of the atmospheric fields in the upper and lower parts of the thunderclouds. 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 yet a commonly accepted explanation. The new view of thunderclouds as media full of radiation can help to establish a comprehensive theory of cloud electrification and estimate the role of cloud radiation in climate change. The influence of the electrified atmosphere on the fluxes of electrons and other charged particles is important for experiments registering very-high energy photons (Systems of Imaging Cherenkov telescopes) and hadrons (Surface arrays registering Extensive Air Showers. TEPA meeting is a great opportunity for the scientists to meet, discuss, invent new ideas and make new bridges for collaborative works.

STRUCTURE OF THE SYMPOSIUM:

 We anticipate the following sessions:

1.       Models of atmosphere electrification and electron acceleration;

          Multivariate observations of particles and fields from the Earth’s surface,

          in atmosphere and    from space (TGEs, gamma glows and TGFs);

2.       Registration of atmospheric discharges by lightning mapping arrays and interferometers;

3.       Influence of the atmospheric electric field on measurements of experiments 

          using atmosphere as a target (Surface Arrays and Cherenkov Imaging Telescopes)

4.       Instrumentation

 

We plan also discussions on the most intriguing problems of high-energy physics in the atmosphere and on possible directions for the advancement of the collaborative studies.

Topics to be covered during oral and poster sessions:

▪        Energy spectra of electrons and gamma rays measured on the earth’s surface, in the atmosphere and in the space;

         their relation to the electron acceleration models;

▪        Possible relations of the Solar activity and space weather to high-energy physics processes in the atmosphere;

▪        Registration of wide- and narrowband radio emissions produced by atmospheric discharges and particle fluxes;

▪        Lightning initiation and its relation to particle fluxes originated in thundercloud (which precede another)?

▪        Neutron and positron production during thunderstorms;

▪        SEVAN East-European particle detector network as a tool for the TGE research;

▪        Methods of the remote sensing of the thundercloud structure and the atmospheric electric field;

▪        Lightning monitoring with fast cameras;

▪        Millisecond length X- and gamma 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;

▪        Influence of the atmospheric electric fields on Extensive Air Shower (EAS) and Cherenkov light.

▪       The possibility of joint observations by space borne and ground-based facilities.

▪       The global electrical circuit.