CR effects in the atmosphere

Measuring atmospheric electric field by the European network of SEVAN detectors

A.Chilingarian1,T.Karapetyan1, G.Karapetyan1, G,Hovsepyan1, B.Sargsyan1, N.Nikolova2,H.Angelov2, Y.Chum3, R.Langer4
1 Artem Alikanyan National Lab (Yerevan Physics Institute), Armenia
2 Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences
3 Czech Republic Atmospheric Physics of the Czech Academy of Sciences, Prague
4 Kosice, Slovakiaxperimental Physics, Slovak Academy of Sciences

Modules of the European SEVAN network located on mountain heights are well suited for the detection of thunderstorm ground enhancements (TGEs) and “stopping muon effect” measured at Aragats (Armenia), Lomnicky Stit (Slovakia) and Musala (Bulgaria). Employing large TGEs as a manifestation of the strong electric field in the thundercloud we measure fluxes of 3 species of secondary cosmic rays(electrons, gamma rays and muons) by SEVAN detectors located in European countries and in Armenia on mountain peaks at heights ≈ 3km. The modulation that electric field poses on charged particle flux gives a sizable change in count rate of detectors measuring high energy muon flux and inclined muon flux in the presence of huge enhancement of electron and gamma ray fluxes in presence of TGE. The muon stopping effect, observed by the SEVAN particle detectors comprises the abrupt decline of count rate of high energy muons (vertical at energies above 200 MeV and inclined. Count rate decreases detected by SEVAN detector has amplitude down to 10% and several minute durations. A simple model of shifting of the energy spectrum of particles entering the electrical field was used to estimate the potential drop of 300-600 MV occurred on high-mountain stations during thunderstorms.

Our estimate was obtained using data from SEVAN detectors measuring fluxes of electrons, gamma rays and neutrons. Our method also used highly enhanced fluxes of TGE gamma rays and electrons, strength of the near surface electric field, cloud height and evidence of lightning flash. Our “multi-sensory” approach included:

  1. Registration of storm with multiple lightning flashes;
  2. Registration of near-surface electric field dropping in negative energy domain after the active phase of the storm;
  3. Registration of huge flux of electrons, gamma rays, and neutrons;
  4. Registration of decline in the intensity of SEVAN “111” combination (~250 MeV muons);
  5. Estimation of the cloud base height above the particle detectors,
  6. Registration of lightning flash abruptly terminating TGE.


Short-term Periodicities Observed in Neutron Monitor Counting Rates

A.López-Comazzi, J.J.Blanco

Neutron monitor counting rates and solar wind velocity, interplanetary magnetic field, sunspot number and total solar irradiance measurements from 2013 to 2018 corresponding to the end of solar maximum and the decreasing phase of the Solar Cycle 24 have been used.
The main objective is to check whether the periodicities observed in the cosmic rays are affected by the magnetic rigidity or the height at which the neutron monitors are placed.
A Global Neutron Monitor (GMN) has been defined as representative of the neutron monitor global network. This GNM is constructed by averaging the counting rates of a set of selected neutron monitors. The selection process is based on the combination three new data quality criteria which are applied to neutron monitors in the Neutron Monitor Data Base giving a final pool of 22 selected neutron monitors. The Morlet wavelet analysis is applied to the GNM and the selected solar activity parameters to find out common periodicities.
Short-term periodicities of 13.5, 27, 48, 92, 132 and 298 days have been observed in cosmic ray intensity. A clear inverse relationship between rigidity and spectral power has been obtained for the 13.5, 48, 92, 132–day periods. A not so clear but still observed direct relationship between the height of the neutron monitors and the spectral power for the 48, 92, 132–day periods has been also found. The periodicity of 92 days is the one which shows the highest dependence with rigidity cutoff and height.
As far as we know, this is the first time that these dependencies are reported. We think that these observations could be explained by assuming some cosmic ray intensity energy dependence in such periodicities and a competitive effect between rigidity and height.


Monitoring Environmental Water with Ground Albedo Neutrons from Cosmic Rays

Martin Schrön, Helmholtz Centre for Environmental Research GmbH - UFZ, Monitoring and Exploration Technologies, Leipzig, Germany,
Markus Köhli, Heidelberg University, Physikalisches Institut, Heidelberg, Germany,

In the last 10 years the young research field of Cosmic-Ray Neutron Sensing for Environmental Sciences has established a technique to monitor local dynamics of water content in soils and snow by measuring the albedo flux of sub-MeV neutrons. The moderation power of water in soil, air, snow and vegetation determines the density of neutrons above the ground in the energy range from 1 eV to 100 keV. The signal represents an area-average water content within tens of hectares due to the diffusion of neutrons in air, and within tens of decimeters in depth. This turns a small neutron detector into a smart sensor for root-zone soil moisture at the field scale. Hundreds of small neutron detectors have been installed on natural and agricultural sites all across the globe. Climate research, hydrologic models and irrigation management rely on this data. A critical factor for the reliability of such data is the knowledge of the dynamics of incoming cosmic-ray neutrons. Conventionally, independent data from neutron monitors are consulted to serve as a reference for the correction of the local detectors. However, the performance of this comparative correction approach is often unreliable, as it does not account for displacement (cutoff rigidity, altitude), different energy window, or potential other effects on the referenced neutron monitor. The presentation shows how ground albedo neutrons from cosmic-rays are applied to environmental research, and emphasizes the need for a reliable correction for the incoming cosmic-ray flux. Being part of a young adjacent community, we rely on the neutron monitor network as our backbone, so we are interested to understand better the data provided by individual instruments and discuss approaches that account for spatio-temporal variations of incoming cosmic rays on Earth. On the other hand, our findings on the response of cosmic-ray neutrons to environmental factors as well as the large network of instruments could open new opportunities for potential cooperations between the disciplines.


Cosmic Radiation Exposure of Aviators for Solar Cycles 23 and 24

Pavlos Paschalis (1), Anastasia Tezari (1),(2), Helen Mavromichalaki (1), Pantelis Karaiskos (2), Norma Crosby (3), Mark Dierckxsens (3)
(1) Athens Cosmic Ray Group, Faculty of Physics, National and Kapodistrian University of Athens, Panepistimioupolis, Zografos, 15784 Athens, Greece,
(2) Medical Physics Laboratory, Faculty of Medicine, National and Kapodistrian University of Athens, 75 Mikras Asias Street, Goudi, 11527 Athens, Greece,
(3) Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Ringlaan-3-Avenue Circulaire, Uccle, Brussels, Belgium 1180

Assessing the radiation exposure of aviators and frequent flyers requires the study of the cosmic ray showers inside the Earth’s atmosphere. DYASTIMA / DYASTIMA-R is a Geant4 based software application, implemented by the Athens Cosmic Ray Group which allows the study of the evolving secondary particles cascades inside the atmosphere, as well as radiation dosimetry calculations (dose, equivalent dose and ambient equivalent dose rates) at different atmospheric altitudes, geographic coordinates and magnetic cut-off rigidity. Results for various scenarios, as calculated by DYASTIMA/DYASTIMA-R, are provided as a federated product through the European Space Agency Space Situational Awareness of the Space Radiation Service Centre Network, while the DYASTIMA software is provided through the Athens Neutron Monitor Station (A.Ne.Mo.S.) portal. Initial results for the assessment of the radiation exposure during the last Solar Cycles 23 and 24 are presented in this work, covering the most usual flying altitudes. The results indicate the dependence of the dose rate on the magnetic cut-off rigidity threshold, with higher dose rates at high geographic latitudes, as well as the anti-correlation of cosmic ray intensity with the solar activity, as higher dose rates are observed during solar minimum conditions.


Comparison between Daejeon neutron monitor data and clouds data during 2012-2018

Jongil Jung, Department of Astronomy, Space Science and Geology, Chungnam National University, Daejeon, Korea; Korea Polar Research Institute, Incheon, Korea
Suyeon Oh, Department of Earth Science Education, Chonnam National University, Gwangju, Korea
Yu Yi, Department of Astronomy, Space Science and Geology, Chungnam National University, Daejeon, Korea

Cosmic ray particles are the high-energy ions, mostly protons to enter the Earth from the space. They can be observed on ground base as the secondary particles produced by colliding with atmospheric particles. This collision process begins at an altitude of approximately 30 km from the ground. Because many neutrons as the secondary particles are generated by interaction with cosmic rays and atmospheric particles, cosmic ray particles are considered as the cloud condensation nuclei in the previous studies. For that reason, we examine the relation between cosmic ray flux and cloud production. We present the result by analyzing the cosmic ray intensity of Daejeon neutron detector operated from October 2011, and cloud data of East Asia in Communication Ocean and Meteorological Satellite (COMS) during the period from 2012 to 2018.