Most cited ARAGATS papers

TITLE


Ground-based observations of thunderstorm-correlated fluxes of high-energy electrons, gamma rays, and neutrons

Authors

A Chilingarian, A Daryan, K Arakelyan, A Hovhannisyan, B Mailyan, L Melkumyan, G Hovsepyan, S Chilingaryan, A Reymers, L Vanyan

Publication date

2010/8/23

Journal

Physical Review D

Volume

82

Issue

4

Pages

043009

Publisher

American Physical Society

Description

The Aragats Space Environmental Center facilities continuously measure fluxes of neutral and charged secondary cosmic ray incidents on the Earth’s surface. Since 2003 in the 1-minute time series we have detected more than 100 enhancements in the electron, gamma ray, and neutron fluxes correlated with thunderstorm activities. During the periods of the count rate enhancements, lasting tens of minutes, millions of additional particles were detected. Based on the largest particle event of September 19, 2009, we show that our measurements support the existence of long-lasting particle multiplication and acceleration mechanisms in the thunderstorm atmosphere. For the first time we present the energy spectra of electrons and gamma rays from the particle avalanches produced in the thunderstorm atmosphere, reaching the Earth’s surface.

Total citations

Cited by 192

 

 

Particle bursts from thunderclouds: Natural particle accelerators above our heads

Authors

Ashot Chilingarian, Gagik Hovsepyan, Armen Hovhannisyan

Publication date

2011/3/1

Journal

Physical review D

Volume

83

Issue

6

Pages

062001

Publisher

American Physical Society

Description

Strong electrical fields inside thunderclouds give rise to fluxes of high-energy electrons and, consequently, gamma rays and neutrons. Gamma rays and electrons are currently detected by the facilities of low orbiting satellites and by networks of surface particle detectors. During intensive particle fluxes, coinciding with thunderstorms, series of particle bursts were detected by the particle detectors of Aragats Space Environmental Center at an altitude of 3250 m. We classify the thunderstorm ground enhancements in 2 categories, one lasting microseconds, and the other lasting tens of minutes. Both types of events can occur at the same time, coinciding with a large negative electric field between the cloud and the ground and negative intracloud lightning. Statistical analysis of the short thunderstorm ground enhancement bursts sample suggests the duration is less than 50 μ s and spatial extension is larger than 1000 m …

Total citations

Cited by 98

 

 

Neutron bursts associated with thunderstorms

Authors

Ashot Chilingarian, Nikolaj Bostanjyan, L Vanyan

Publication date

2012/4/16

Journal

Physical review D

Volume

85

Issue

8

Pages

085017

Publisher

American Physical Society

Description

The basis of our analysis is the observation of the simultaneous enhancements of the gamma ray and neutron fluxes detected in 2009–2010 during thunderstorm ground enhancements at the mountain altitude of 3200 m. We investigate the correlated time series of the gamma rays and neutrons measured by the surface particle detectors of Aragats Space Environmental Center. The photonuclear reactions of the gamma rays born in the runaway breakdown (RB, now referred to as relativistic runaway electron avalanche, RREA) process with air were considered as the main process responsible for the copious neutron production. We consider also the mesoatom nuclei decay as a possible source of the additional neutrons registered by the neutron monitor due to enhanced population of the negative muons accelerated in the thunderclouds.

Total citations

Cited by 68

 

Statistical decisions under nonparametric a priory information

Authors

AA Chilingarian

Publication date

1989/6/1

Journal

Computer Physics Communications

Volume

54

Issue

2-3

Pages

381-390

Publisher

North-Holland

Description

A program is developed for simular and experimental data handling. The main purposes are: the choice of the model most precisely describing the experiment, classification of particles and interaction processes. Procedures used: Bayes error calculation, K nearest neighbour density estimation, “Leave-one-out-at-a-time” test. Used nonparametric methods provide quantitative comparison of multivariate distribution mixture classification. Applications: high energy physics, cosmic ray physics.

Total citations

Cited by 64

 

 

Multivariate approach for selecting sets of differentially expressed genes

Authors

A Chilingaryan, N Gevorgyan, A Vardanyan, D Jones, A Szabo

Publication date

2002/3/1

Journal

Mathematical Biosciences

Volume

176

Issue

1

Pages

59-69

Publisher

Elsevier

Description

An important problem addressed using cDNA microarray data is the detection of genes differentially expressed in two tissues of interest. Currently used approaches ignore the multidimensional structure of the data. However it is well known that correlation among covariates can enhance the ability to detect less pronounced differences. We use the Mahalanobis distance between vectors of gene expressions as a criterion for simultaneously comparing a set of genes and develop an algorithm for maximizing it. To overcome the problem of instability of covariance matrices we propose a new method of combining data from small-scale random search experiments. We show that by utilizing the correlation structure the multivariate method, in addition to the genes found by the one-dimensional criteria, finds genes whose differential expression is not detectable marginally.

Total citations

Cited by 58

 

 

Thunderstorm ground enhancements—Model and relation to lightning flashes

Authors

A Chilingarian

Publication date

2014/1/1

Journal

Journal of Atmospheric and Solar-Terrestrial Physics

Volume

107

Pages

68-76

Publisher

Pergamon

Description

In the beginning of last century C.T.R. Wilson proposed that strong electric field of the thunderclouds might accelerate electrons to very high energies. However, this and many other electromagnetic processes in our atmosphere are poorly understood till now; the key questions about the thundercloud electrification and lightning initiation remain unanswered. During recent decades several observations of gamma ray, electron and neutron fluxes correlated with thunderstorms were reported. Nonetheless, the origin of these fluxes is under debate till now. The direct registration of the particle showers initiated by the runaway electrons (the most popular theory) was missing. We present the experimental evidence of the microsecond duration electron bursts originated from runaway electrons accelerated in thunderclouds. The electron acceleration downward becomes possible after creation of the Lower Positive Charged …

Total citations

Cited by 55

 

 

Role of the lower positive charge region (LPCR) in initiation of the thunderstorm ground enhancements (TGEs)

Authors

A Chilingarian, H Mkrtchyan

Publication date

2012/10/8

Journal

Physical Review D

Volume

86

Issue

7

Pages

072003

Publisher

American Physical Society

Description

Despite the ubiquity of thunderstorms, lightning, and related electrical phenomena, many important electromagnetic processes in our atmosphere are poorly understood; the key questions about the thundercloud electrification and lightning initiation remain unanswered. The bulk information on particle fluxes correlated with thunderstorm can be used to better understand the electrical structure of thunderclouds. Only very specific electric configuration of the lower part of the cloud can support the sustainable acceleration of the electrons. Our analysis is based on the thunderstorm data from the Aragats Mountain in Armenia, 3200 m above sea level Varieties of particle detectors located at Aragats Space Environmental Center are registering neutral and charged particle fluxes correlated with thunderstorms, so-called Thunderstorm Ground Enhancements (TGEs). Simultaneously the electrical mills and lightning detectors …

Total citations

Cited by 43

 

 

Thunderstorm ground enhancements: Gamma ray differential energy spectra

Authors

A Chilingarian, G Hovsepyan, L Kozliner

Publication date

2013/10/1

Journal

Physical Review D

Volume

88

Issue

7

Pages

073001

Publisher

American Physical Society

Description

The shape and evolution of the energy spectra of the thunderstorm ground enhancement (TGE) electrons and gamma rays shed light on the origin of TGEs, on the relationship of modification of the energy spectra (MOS) and relativistic runaway electron avalanche processes, on the nature of the seed particles, and on the strength and elongation of an atmospheric electric field. However, till now the measurements of energy spectra of TGE electrons and gamma rays have been rather scarce. For the first time, we present differential energy spectra of gamma rays in the wide energy range 4–100 MeV for five TGE events detected in 2012–2013 at Aragats. We use the special technique of electron/gamma ray fraction determination to select TGE events with very small contamination of electrons. The network of large NaI spectrometers located 3200 m above sea level measured energy spectra of gamma rays. The power …

Total citations

Cited by 37

 

Study of extensive air showers and primary energy spectra by MAKET-ANI detector on mountain Aragats

Authors

A Chilingarian, G Gharagyozyan, S Ghazaryan, G Hovsepyan, E Mamidjanyan, L Melkumyan, V Romakhin, A Vardanyan, S Sokhoyan

Publication date

2007/9/1

Journal

Astroparticle Physics

Volume

28

Issue

1

Pages

58-71

Publisher

North-Holland

Description

Small and middle size surface detectors measuring extensive air showers (EAS) initiated by primary cosmic rays (PCR) incident on terrestrial atmosphere have been in operation for the last 50 years. Their main goal is to explore the “knee” in all particle spectrum to solve the problem of cosmic ray (CR) origin and acceleration. The recent achievements of atmospheric Cherenkov telescopes and X-ray space laboratories, establishing the supernova remnants (SNRs) as a source of hadronic cosmic rays, pose stringent conditions on the quality of EAS evidence. After establishing the existence of the “knee” itself, the most pronounced result from EAS studies is the rigidity dependent shift of the knee position to the highest energies. This feature was first observed by separation of the primary flux in different mass groups in MAKET-ANI, EAS-TOP and KASCADE experiments. The MAKET-ANI detector is placed on Mt …

Total citations

Cited by 36

 

On the production of highest energy solar protons at 20 January 2005

Authors

N Kh Bostanjyan, AA Chilingarian, VS Eganov, GG Karapetyan

Publication date

2007/1/1

Journal

Advances in Space Research

Volume

39

Issue

9

Pages

1454-1457

Publisher

Pergamon

Description

On January 20, 2005, 7:02–7:05 UT the Aragats Multidirectional Muon Monitor (AMMM) located at 3200 m a.s.l. registered enhancement of the high energy secondary muon flux (threshold 5 GeV). The enhancement, lasting for 3 min, has statistical significance of 4σ and is related to the X7.1 flare seen by the GOES, and very fast (>2500 km/s) CME seen by SOHO, and the Ground Level Enhancements (GLE) #69 detected by the world-wide network of neutron monitors and muon detectors. The energetic and temporal characteristics of the muon signal from the AMMM are compared with the characteristics of other monitors located at the Aragats Space-Environmental Center (ASEC) and with other neutron and muon detectors. Since secondary muons with energies >5 GeV are corresponding to solar proton primaries with energies 20–30 GeV we conclude that in the episode of the particle acceleration at 7:02–7:05 …

Total citations

Cited by 32

 

Investigations of the response of hybrid particle detectors for the Space Environmental Viewing and Analysis Network (SEVAN)

Authors

A Chilingarian, A Reymers

Publication date

2008/2/26

Journal

Annales Geophysicae

Volume

26

Issue

2

Pages

249-257

Publisher

Copernicus GmbH

Description

A network of particle detectors located at middle to low latitudes known as SEVAN (Space Environmental Viewing and Analysis Network) is being created in the framework of the International Heliophysical Year (IHY-2007). It aims to improve the fundamental research of the particle acceleration in the vicinity of the Sun and space environment conditions. The new type of particle detectors will simultaneously measure the changing fluxes of most species of secondary cosmic rays, thus turning into a powerful integrated device used for exploration of solar modulation effects. Ground-based detectors measure time series of secondary particles born in cascades originating in the atmosphere by nuclear interactions of protons and nuclei accelerated in the galaxy. During violent solar explosions, sometimes additional secondary particles are added to this "background" flux. The studies of the changing time series of secondary particles shed light on the high-energy particle acceleration mechanisms. The time series of intensities of high energy particles can also provide highly cost-effective information on the key characteristics of interplanetary disturbances. The recent results of the detection of the solar extreme events (2003–2005) by the monitors of the Aragats Space-Environmental Center (ASEC) illustrate the wide possibilities provided by new particle detectors measuring neutron, electron and muon fluxes with inherent correlations. We present the results of the simulation studies revealing the characteristics of the SEVAN networks' basic measuring module. We illustrate the possibilities of the hybrid particle detector to measure neutral and charged …

Total citations

Cited by 31

 

 

Lightning origination and thunderstorm ground enhancements terminated by the lightning flash

Authors

A Chilingarian, G Hovsepyan, G Khanikyanc, A Reymers, S Soghomonyan

Publication date

2015/6/11

Journal

EPL (Europhysics Letters)

Volume

110

Issue

4

Pages

49001

Publisher

IOP Publishing

Description

Proceeding from the measurements of the lightning occurrences, slow and fast electric-field disturbances, particle flux enhancements and their abrupt terminations, we formulate a lightning origination model. Registration of the extensive air shower simultaneously with lightning detection allows us to propose a solution to the long-standing problem of its role in the lightning initiation. Our analysis is based on the numerous Thunderstorm Ground Enhancements detected in 2012–2014 at Mt. Aragats in Armenia.

Total citations

Cited by 29

 

 

On the possibility of investigation of the mass composition and energy spectra of primary cosmic ray (PCR) in the energy range from 1015 to 1017 eV using EAS data

Authors

AA Chilingarian, GZ Zazian

Publication date

1991/11/1

Journal

Il Nuovo Cimento C

Volume

14

Issue

6

Pages

555-568

Publisher

Kluwer Academic Publishers

Description

A method allowing one to determine the mass composition of primary cosmic radiation by means of simultaneous analysis of model and experimental data is presented in this paper. The most important part of this work is the quantitative comparison of multivariate distributions and the use of methods of nonparametric statistics for probability density estimation in a multivariate space of features. To check the method offered, events withE 0>500TeV were generated by the Monte Carlo method. The showers generated were preliminarily processed by algorithms used in experimental data handling. The apparatus-induced distortions of the measured EAS characteristics have been taken into account. The method allows one to select an experimental event initiated by primary protons and iron nuclei with an efficiency of (70÷80)%. Also a new multivariate method of incident particle energy estimation …

Total citations

Cited by 29

 

Mount Aragats as a stable electron accelerator for atmospheric high-energy physics research

Authors

Ashot Chilingarian, Gagik Hovsepyan, Eduard Mnatsakanyan

Publication date

2016/3/7

Journal

Physical Review D

Volume

93

Issue

5

Pages

052006

Publisher

American Physical Society

Description

Observation of the numerous thunderstorm ground enhancements (TGEs), ie, enhanced fluxes of electrons, gamma rays, and neutrons detected by particle detectors located on the Earth’s surface and related to the strong thunderstorms above it, helped to establish a new scientific topic—high-energy physics in the atmosphere. Relativistic runaway electron avalanches (RREAs) are believed to be a central engine initiating high-energy processes in thunderstorm atmospheres. RREAs observed on Mount Aragats in Armenia during the strongest thunderstorms and simultaneous measurements of TGE electron and gamma-ray energy spectra proved that RREAs are a robust and realistic mechanism for electron acceleration. TGE research facilitates investigations of the long-standing lightning initiation problem. For the last 5 years we were experimenting with the “beams” of “electron accelerators” operating in the …

Total citations

Cited by 27

 

Remarks on recent results on neutron production during thunderstorms

Authors

A Chilingarian, N Bostanjyan, T Karapetyan, L Vanyan

Publication date

2012/11/13

Journal

Physical Review D

Volume

86

Issue

9

Pages

093017

Publisher

American Physical Society

Description

We analyze the neutron fluxes correlated with thunderstorm activity recently measured at mountain altitudes by the Tien-Shan, Tibet, and Aragats groups. We perform simulations of the photonuclear reactions of gamma rays born in the electron-gamma ray avalanches and calculate the expected count rates of the neutron detectors used by the three groups. We also present results of an independent experiment performed at the Nor Amberd high altitude research station in Armenia. Our analysis supports the Tibet and Aragats groups’ conclusions on the photonuclear nature of thunderstorm-correlated neutrons (directly in the neutron monitor and in the atmosphere). The photonuclear reactions of the gamma rays born in the electron-photon avalanches in the thunderstorm atmospheres interacting with the air atoms and with lead producer of a neutron monitor can provide neutron yield compatible with additional count …

Total citations

Cited by 27

 

 

A multidimensional analysis of the Cherenkov images of air showers induced by very high energy γ-rays and protons

Authors

FA Aharonian, AA Chilingarian, AK Konopelko, AV Plyasheshnikov

Publication date

1991/5/1

Journal

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Volume

302

Issue

3

Pages

522-528

Publisher

North-Holland

Description

A multidimensional analysis based on Bayes decision rules and nonparametric multivariate density estimation is proposed for classification of the Cherenkov light images of air showers registered by an air Cherenkov detector (ACD) with the multichannel light receiver. The differences in the angular size of the image, its orientation and position in the focal plane of the ACD and spectral composition of the Cherenkov light are used in the analysis to distinguish the showers induced by primary γ-rays from showers induced by background cosmic rays (CR). It is shown that the usage of several image parameters together with their correlations can lead to a reduction of the CR background rejection down to a few tenths of a percent while retaining about 50% of useful (γ-ray-induced) events.

Total citations

Cited by 26

 

The system of imaging atmospheric Cherenkov telescopes: The new prospects for VHE gamma ray astronomy

Authors

FA Aharonian, AA Chilingarian, RG Mirzoyan, AK Konopelko, AV Plyasheshnikov

Publication date

1992/11

Journal

Experimental astronomy

Volume

2

Issue

6

Pages

331-344

Publisher

Kluwer Academic Publishers

Description

Using Monte Carlo simulations the possibilities are investigated for registration of VHE gamma radiation by means of systems of imaging air Cherenkov telescopes (IACT). It is shown that even a system of IACT's with moderate properties (three telescopes with the geometrical area of the optical reflector≈5 m 2and the angular size of the pixel≈0.41 0 ) could provide the energy resolution 20–25% and achieve the sensitivity (minimum detectable flux) up to 10-12 photon/cm 2s at the effective energy threshold ≈1 TeV.

Total citations

Cited by 24

 

Types of lightning discharges that abruptly terminate enhanced fluxes of energetic radiation and particles observed at ground level

Authors

A Chilingarian, Y Khanikyants, E Mareev, D Pokhsraryan, VA Rakov, S Soghomonyan

Publication date

2017/7/27

Journal

Journal of Geophysical Research: Atmospheres

Volume

122

Issue

14

Pages

7582-7599

Description

We present groundbased measurements of thunderstormrelated enhancements of fluxes of energetic radiation and particles that are abruptly terminated by lightning discharges. All measurements were performed at an altitude of 3200 m above sea level on Mount Aragats (Armenia). Lightning signatures were recorded using a wideband electric field measuring system with a useful frequency bandwidth of 50 Hz to 12 MHz and network of five electric field mills, three of which were installed at the Aragats station, one at the Nor Amberd station (12.8 km from Aragats), and one at the Yerevan station (39 km from Aragats). We observed that the fluxenhancement termination was associated only with close (within 10 km or so of the particle detector) negative CGs and normalpolarity ICs; that is, with lightning types which reduce the upward directed electric field below the cloud and hence suppress the acceleration of …

Total citations

Cited by 23