The first years of Armenia's independence were very difficult for the staff at Yerevan Physics Institute’s Cosmic Ray Division (CRD). With funding suddenly stopped from the largest soviet ministry, there was no fuel, electricity, and food. Monthly salaries were the equivalent of five U.S. dollars. The construction of the world’s largest cosmic ray experiment, ANI1, remained half-completed. Work on the detectors ceased, and a question arose: “Is it really necessary to continue this research on Aragats? Will it be possible?” How could our research stations keep working on Mt. Aragats’ severe high-mountain winter conditions?

After a year of shock, CRD physicists adopted a realistic program for future research. They would continue measurements of high-energy cosmic rays and establish new research directions where CRD could be a world leader. They would conduct research that would not require abundant funds for constructing expensive, gigantic experiments. The key part of this program was CRD’s participation in international projects, submitting proposals for international funding, and establishing close ties with the Armenian diaspora in the USA.

During the initial five years, these hard efforts produced positive results. In collaboration with Russia’s Lebedev institute, two arrays of particle detectors to measure extensive air showers of cosmic ray particles were completed. These detectors, named “GAMMA” and “MAKET ANI”, consisted of more than three hundred scintillation detectors that measured fluxes of almost all species of cosmic rays and gigantic particle showers initiated by ultra-high energy particles accelerated in our Galaxy and beyond.

CRD participated in a worldwide collaboration with Japan’s Nagoya University, the German nuclear centers at Karlsruhe, and the Max Plank Institute Fur Physics in Munich. CRD physicists won grants totaling $2.5 million. New particle detectors and advanced electronics were designed, fabricated, and commissioned. Modern software for data storage and for making physical inferences was created. Neutron monitors were reoperated with modern electronics at Nor Amberd and Aragats research stations at 2.0 km and 3.2 km altitudes respectively. 

In the new scientific field of solar physics and space weather research, CRD physicists produced rapid results, making important measurements, publishing their initial scientific papers, and joining the International Heliophysical Year (IHY) – managed by the UN’s agency of outer space research. CRD participated as a leading group in developing networked particle detectors to be installed in developing countries. This was one of the most successful IHY programs and is continuing, with SEVAN2 nodes located in Armenia, Bulgaria, the Czech Republic, Croatia, Germany, and Slovakia with a total of 10 detectors.

1 ANI – Research of Cosmic Ray hadrons on the earth’s surface – joint experiment with Lebedev Physical Institute of Soviet Academy of Sciences.

2 SEVAN - Space Environmental Viewing and Analysis Network.

In 2009 CRD scientists revealed electron accelerators operated in the thunderclouds above Aragats, registering intense particle bursts from electron-photon avalanches developing in thunderous atmosphere. This physical phenomenon was called Thunderstorm Ground Enhancement – TGE, and now tens of groups around the world are registering TGE. Aragats physicists were the first to measure the energy spectra of electrons and gamma rays from particle avalanches of atmospheric origin that reach the Earth's surface. 

Figure 1. Mt. Aragats, MAKET-ANI detector researching physics around the “knee”, the first observation of the light and heavy Galactic nuclei energy spectra was done on Aragats.

Figure 2. Gagik Hovsepyan examined data from the Aragats Solar Neutron Telescope (ASNT) designed for the detection of neutrons from solar flares in collaboration with Professor Yasushi Muraki (Nagoya University).

Also, for the first time, CRD scientists observed the light glows emitted during the development of electron-gamma cascades in the atmosphere, which was well correlated with the high-energy electron flux registered by surface particle detectors. Thus, they first discover TGE phenomena by detecting simultaneous fluxes of high energy electrons, gamma rays, and neutrons; then they observed Relativistic Runaway Electron Avalanches (RREA) by detecting particle showers coming from the clouds. Subsequently, they proved the existence of the lower dipole that accelerated electrons toward the Earth’s surface. Simulations of electron propagation in the strong atmospheric electric fields, and estimation of the maximum voltage in the charged atmosphere, reveal the origin of this phenomenon. Only then did CRD present a comprehensive model of TGEs and evidence of RREA’s origination in the atmosphere. Simultaneously Bulgaria, Croatia, Czech Republic, Germany, and Slovakia, all using SEVAN detectors, contributed to a better understanding of the high-energy physics in the atmosphere. They also contributed to the study of vertical profile in electron-positron and gamma components produced during thunderstorms.

Figure 3: Bagrat Mailyan, Gagik Hovsepyan, Levon Vanyan, Ashot Chilingarian, Nikolaj Bostanjyan (CRD physicists), the group that received Armenia president prize for achievements in establishing high-energy atmospheric physics, 2012.

CRD’s SEVAN detectors are unique devices that can observe the modulation of particle fluxes due to violent outbursts from the Sun, forecast dangerous consequences of space weather, and perform wide research programs in the fundamental aspects of atmospheric physics.

Figure 3. Balabek Sargsyan and Tigran Karapetyan installing SEVAN detector at DESY, Zeuthen, Germany.

The operation of the SEVAN network in 2021-2022 revealed new exciting results. Electron energy spectra indicate very large electric fields (of up to 200 kV/m) near the Earth's surface (50-150 m), which can affect the safety of rocket launches and aircraft operations during thunderstorms. On September 12, 2021, the SEVAN detector on Lomnicky Štít (Slovakia) measured a 500% enhancement of particle fluxes. The world-largest TGE, with particle fluxes exceeding the normal rates by 100 times, also was measured by the Slovakian SEVAN detector in 2017.

Now research on Aragats encompasses the most interesting aspects in the fast-developing atmospheric, solar, and high-energy physics. This includes cosmic ray origin; solar-terrestrial connections; solar modulation of galactic cosmic rays; space weather; acceleration of particles on the sun; high-energy physics in the atmosphere; lightning physics; and multivariate data analysis. Particle fluxes measured by spatially scattered networks, combined with information from satellites, provide experimental data on the most energetic processes on the Sun and in the Earth's atmosphere. This will become an important element of global space weather monitoring and forecasting services.