On-line database of cosmic ray intensities (original) (raw)
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Athens Neutron Monitor and its aspects in the cosmic-ray variations studies
2001
After many years break (since the 1978) the Athens Neutron Monitor renewed its operation due to joint efforts of Athens University (Greece) and IZMIRAN (Russia). In the present work the short history of this station and the modernization of the neutron monitor registration system, which made possible the real time presentation of current measurements in the Worldwide Network are described. The main properties and some advantages of this station in comparison with others are considered in the aspect of using its data for the Solar-Terrestrial and Space Weather studies.
RESPONSE OF NEUTRON MONITORS TO COSMIC RAY COUNTS: A STATISTICAL APPROACH
Study of cosmic ray became a subject of study with the invention of neutron monitor by Simpson. But recording of cosmic ray counts was started regularly from International Geophysical Year at different locations having different climatic zones over the globe. Here statistical analysis is performed to investigate the degree of response of different monitors towards cosmic ray counts. No significant difference is observed in statistical analysis if cosmic ray counts are normalized with respect to their mean counts in respective solar cycles. Correlation between cosmic ray counts of any two stations is found ranges from 0.88 to 0.99. Keywords: Cosmic ray, cut off rigidity, Mean absolute deviation, Mean bias error, Uncertainty parameter 1. Introduction At sea level cosmic rays comprise from the extensive air shower. Muons having life time 2µs are the major components which can penetrate the atmosphere and lose energy by ionization. Electrons are generated from the decay of muon and have low penetrating power because of bremsstrahlung loss. Low energy neutrons <10 Mev are produced from excited nuclei while high energy protons are from knock-on collision [Svensmark et al (2007); Tinsley et al, (2007)]. The galactic cosmic ray flux at sea level is not constant. Their intensity is modulated by the 11 year solar cycle, Solar cosmic rays are accelerated during CME but due to sharp energy spectrum, a small fraction of solar cosmic rays with energy > 1 GeV may produce enhancement of ground level energy. During the declining phase of solar cycle magnetospheric electron precipitation occurs. Cosmic ray studies became the growing concerned from the last decades because they are the major sources of (e +-e-) pair production at altitudes ranges from about 4-50 km. Ionization produced by cosmic rays have influenced many processes such as aerosol formation, cloud cover, precipitation, mesoscale dynamics, nucleation process, global electric circuit etc. But no direct measurements were conducted to identify cosmic rays till 1930. It was only known that an electric field exists in fair weather atmosphere. Routine air conductivity measurements were started in]. After that in 1930 a ground based cosmic ray monitor was developed and data was available but the main drawback was uncontrolled instrumental drift arising from radioactive contamination. At last in 1948 worldwide ground based neutron monitor was developed by Simpson and it can detect cosmic rays penetrating the atmosphere with energy ranges from 0.5-20 GeV. It was the standard detector to study cosmic ray variation from IGY (International Geophysical year) which was replaced by NM 64 designed by Carmichael from the International Quiet Sun year 1964[Bhattacharya et al (2013)]. Neutron monitor consists of BF 3 (Boron tri fluoride) gas filled proportional counter enriched with 96% 10 B isotope at 0.27 bar and surrounded by moderator consisting of 2cm thick polyethylene, lead producer (to increase count rate 156 gm/cm 2) and a reflector consisting of 7.5 cm thick polyethylene. The counting rate depends on geomagnetic latitude, altitude and the design of monitor. The fluxes of galactic cosmic ray are modulated when they enter the heliosphere due to the presence of magnetic field and solar wind. Moreover geomagnetic field is the discrimination of charged particle. Particle rigidity is the key governing factor of the motion of the charged particle. Particles having rigidity less than cut off rigidity are unable to reach the investigating place [Fujimoto et al (1976); Cooke et al, (1991); Cattani et al, (2003)]. Particle rigidity (R) is expressed by the equation R. Bhattacharya et al. / International Journal of Engineering Science and Technology (IJEST)
Author ' s personal copy Applications and usage of the real-time Neutron Monitor Database q
2011
A high-time resolution Neutron Monitor Database (NMDB) has started to be realized in the frame of the Seventh Framework Programme of the European Commission. This database will include cosmic ray data from at least 18 neutron monitors distributed around the world and operated in real-time. The implementation of the NMDB will provide the opportunity for several research applications most of which will be realized in real-time mode. An important one will be the establishment of an Alert signal when dangerous solar cosmic ray particles are heading to the Earth, resulting into ground level enhancements effects registered by neutron monitors. Furthermore, on the basis of these events analysis, the mapping of all ground level enhancement features in near real-time mode will provide an overall picture of these phenomena and will be used as an input for the calculation of the ionization of the atmosphere. The latter will be useful together with other contributions to radiation dose calculat...
Simulated effects at neutron monitor energies: evidence for a 22-year cosmic-ray variation
Astronomy & Astrophysics - ASTRON ASTROPHYS, 1998
Determined systematic differences in the overall shapes of successive 11-year modulation cycles (1946-1995) and similarities in the shapes of alternate 11-year cycles seem to be related to the 22-year magnetic cycle and to the polarity reversals of the polar magnetic field of the Sun. This different behaviour of the odd and even solar cycles that are the two parts of the 22-year periodicity is discussed in terms of different processes influencing the transport of cosmic rays from the edges of the heliosphere to the near-Earth region. Taking into account these characteristic features, monthly cosmic-ray data from Inuvik and Climax Neutron Monitor Stations have been used to describe on a general basis the long-term modulation of galactic cosmic-rays during the last three solar cycles (1965-1994) where data are available. With the aid of appropriate selected source functions and calculating the time lag of cosmic-ray intensity against these indices, the modulated cosmic-ray intensity h...
The neutron monitor (NM) remains the best available instrument for monitoring the secondary nucleonic component of the galactic cosmic rays for more than 80 years. Recently, NMs have been given another role related to satellite-based technologies for monitoring and forecasting of space weather events. At many sites around the world, the old neutron monitors were being refurbished and their operation synchronised to form a network known as the neutron monitor data base (NMDB). During the years, little has been changed in the construction of the actual neutron monitor. In this work we carried out a detailed study of the role of the various components (reflector, producer and moderator) on the output signal of a NM64 neutron monitor. The study was performed using the fully integrated particle physics Monte Carlo simulation package, FLUKA, utilising several different types of incident particles - from monoenergetic neutrons and protons to a complex galactic cosmic rays source tailored f...