Journal: The Astrophysical Journal

Download 395.33 Kb.
Date conversion18.07.2017
Size395.33 Kb.
1   2   3   4   5   6   7
80) (6)

Journal: American Institute of Physics: Conference Proceedings

Title: Neutron Monitoring: Past, Present, and Future
General Information: Published online 07 February 2013
Author(s): John William Bieber
Abstract: Ground-based detectors were instrumental in establishing the nature of cosmic rays in the early days of the field, and they continue to provide invaluable information now and for the foreseeable future. This article begins with homage to Scott Forbush and the fundamental discoveries he made with the Carnegie Institution ionization chambers in the 1930s and 1940s. Circa 1950 John Simpson invented the neutron monitor, an instrument more capable, sensitive, and stable than the ionization chamber. An early landmark of the neutron monitor era was the famous 1956 solar cosmic ray event that proved diffusion theory is essential for describing charged particle transport in space. In the modern era, the instrument of choice is an array. The days are gone when a lone neutron monitor placed anywhere on Earth can make discoveries. Now and in the future, science with neutron monitors will require coordinated arrays of detectors that enable continuous, realtime measurement of the cosmic ray directional distribution and energy spectrum. An emerging application for neutron monitors is in the field of space weather prediction and specification, especially as concerns major radiation hazard from solar particles.

81) (7)

Journal: Solar Neutrons and Related Phenomena
Title: Observations of Solar Neutron Events by Ground based Detectors, and Their Interpretation
General Information: Published 23 May 2013, Volume 365 of the series Astrophysics and Space Science Library, Pages 185-350
Author(s): Lev I. Dorman
Abstract: According to Aushev et al. (1999), the Tyan Shan high altitude neutron monitor has a favourable location and good data statistics for solar neutron observations; however, only one enhancement of June 15, 1991 has been attributed to primary solar neutrons during 1976–1998 years. The work of Aushev et al. (1999) presents a search for other possible solar neutron events in the Tyan Shan NM data. The catalogue of major x-ray events registered by the GOES satellites and the available information on the hard x-ray and gamma solar emission obtained aboard the SMM and CGRO satellites were used in this search. For each event from the catalogue, Aushev et al. (1999) calculated an expected response of the Alma-Ata neutron monitor to the flux of solar neutrons like that observed on June 3, 1982. Possible candidates were chosen by comparing expectations with the real NM count rate. Some particular candidates and the statistics of the NM count rate close to onset of energetic solar events are discussed.

82) (8)

Journal: Geomagnetism and Aeronomy
Title: Long-Period Variations in the Amplitude-Phase Interrelation of the First Cosmic Ray Anisotrophy Harmonic
General Information: Published September 2013, Volume 53, Issue 5, Pages 561-570
Author(s): M. A. Abunina, A. A. Abunin, A. V. Belov, E. A. Eroshenko, V. A. Oleneva, V. G. Yanke
Abstract: The distinguished directions, dependent on the solar wind velocity and IMF line position, exist in the interplanetary space, which results in the nonuniform distribution of phases and the amplitude-phase interrelation of the first cosmic ray anisotropy harmonic. The characteristics of the first anisotropy harmonics, determined for each hour using the global survey method based on the worldwide neutron monitor network from 1957 to 2010, were used to study long-period variations in the cosmic ray anisotropy. The longitudinal distributions of the cosmic ray vector anisotropy and the interrelation between the anisotropy amplitude and phase have been obtained for each year in this time interval. The results evidently demonstrate the anisotropy variations caused by the solar magnetic and activity cycles. The anisotropy distributions at different solar wind velocities have also been studied. Periods with a specific cosmic ray anisotropy behavior are distinguished and discussed. The obtained cosmic ray anisotropy variations agree with the convection-diffusion anisotropy model.

83) (9)

Journal: American Institute of Physics: Conference Proceedings
Title: The Descent of the Solar Cycle 24 Cosmic Ray Modulation
General Information: Published online 13 June 2013
Author(s): H. S. Ahluwalia, R. C. Ygbuhay
Abstract: The descending phase of the galactic cosmic ray (GCR) modulation at earth orbit, for the sunspot number (SSN) cycle 24 is studied, using data from the global network of neutron monitors and the balloon measurements at high latitudes in Russia. The decrease in intensity, two years after the onset of modulation, is modest compared to earlier cycles. The tilt angle of the heliospheric current sheet is very close to its maximum value for a cycle and the solar polar field has reversed in the northern hemisphere. So, one should expect the GCR modulation to be close to its maximum value. A preliminary determination is made of the rigidity dependence of the observed modulation for two years. It is a power law with an exponent −1.11, similar to that observed for earlier cycles (20-23).


Journal: American Institute of Physics: Review of Scientific Instruments
Title: Validation of Neutron Emission Profiles in MAST with a Collimated Neutron Monitor
General Information: Published online 27 July 2012, Volume 83, Issue 10
Author(s): S. Sangaroon, M. Cecconello, S. Conroy, M. Weiszflog, M. Turnyanskiy, I. Wodniak, G. Ericsson
Abstract: A neutroncamera with liquid scintillator detectors is used in MAST to measure the neutron emissivity from D(d,n)3He reactions along collimated lines of sight. In this work, the measured recoil proton pulse height spectra generated in the detectors by the incident neutrons is modelled taking into account the energy spectrum of the generated neutrons, their spatial distribution and transport to the detectors as well as the detector's response function. The contribution of scattered neutrons to the pulse height spectrum is also modelled. Good agreement is found between the experimental data and the simulations. Examples are given showing the sensitivity of the recoil proton pulse height spectra to different observation angles with respect the neutral beam injection and the plasma rotation direction.

85) (2)

Journal: American Institute of Physics: Conference Proceedings
Title: Neutron Sources for Test and Calibration of Neutron Detectors for Space Research
General Information: Published online 29 February 2012
Author(s): C. Granja, M. Kralik, Z. Kohout, P. Masek, S. Pospisil, M. Solar, J. Solc, Z. Vykydal, A. Owens, J. Vacik, D. Chvatil, P. Bem, P. Krist, J. Stursa, V. Rypar
Abstract: This work reports on the current status of neutron sources in the Czech Republic as calibrated and ESA compliant stations for space related applications such as the testing and calibration ofneutron detectors and neutron sensitive devices as well as for studies of radiation effects of electric and electronic components. The work was carried out as part of the preparatory accession activities of the Czech Republic with ESA. The goal and one of the tasks is to test and evaluate neutron sensitive devices, both conventional and prototypes, developed at ESA and at the IEAP CTU Prague. The facilities consist of both fast and thermal neutron sources providing testing and absolute calibration of a wide range of neutron detectors. The evaluation and calibration of the sources were carried out in cooperation with the Nuclear Physics Institute, Academy of Sciences of the Czech Republic, the Research Center Rez, and the Czech Metrology Institute in Prague.

86) (3)

Journal: Journal of the Korean Physical Society
Title: Characteristics of the 18-Tube NM64-Type Daejeon Neutron Monitor in Korea
General Information: Published September 2012, Volume 61, Issue 5, Page 720-729
Author(s): Jeongsoo Kang, Doh Yun Jang, Yunho Kim, Byoung Hwi Kang, Yong-Kyun Kim , Jungho Kim, Hyeonseo Park, Yu Yi
Abstract: The amount of cosmic radiation entering Earth’s atmosphere is determined by, and is therefore an indicator of, the level of solar activity. As solar activity approaches a maximum, the importance of monitoring cosmic rays and researching their effects and our dose levels increases. The aim of this study was to install the NM64 neutron monitor and to measure its characteristics by using two different methods: analyzing the barometric coefficient and observing the diurnal variation. A neutron monitor was installed for the first time in Korea at the Korea Research Institute of Standard Science in 2011 with a rigidity cutoff of 11.2 GV. The barometric coefficient and the diurnal variation were analyzed with data for the interval Dec. 1–31, 2011. A reliable barometric coefficient was determined, −0.6557 ± 0.0044%/hPa, and the diurnal variation was observed. The Daejeon neutron monitor worked correctly, given that the diurnal variation was hard to observe when the variation was small (in this case, less than 1%).
Hyperlink: Full Text not Available

87) (4)

Journal: Journal of the Korean Physical Society
Title: Cosmic Ray Measurement and Experimental Temperature Analysis with a Muon Detector
General Information: Published August 2012, Volume 61, Issue 4, Page 647-652
Author(s): Yun Ho Kim, Jeongsoo Kang, Doh-Yun Jang, Jae Bum Son, Yong-Kyun Kim
Abstract: The Basic Atomic Energy Research Institute (BAERI) of Hanyang University in Korea constructed and operates a cosmic ray detection system. In this study, a muon detector composed of a plastic scintillator and a wavelength shifter was used to obtain data over a total of six experimental periods. Using the collected data, we analyzed the response dependence of the developed muon detector on the laboratory’s environmental temperature. The detection results showed a correlation coefficient of over 0.7, as well as a negative proportional correlation in the experiments in which the thermostat did not operate. We performed a correction for the laboratory’s environmental temperature and analyzed the correlation between the muon count rate and the atmospheric pressure. As a result, we obtained a barometric coefficient of −0.1191 ± 0.0054%/hPa. The analyzed data were compared with data from the eighteen NM64 type neutron monitors at our station. The correlation coefficient between the two detection systems was approximately 0.8046, confirming that the response changes were roughly identical to response of neutron monitors.
Hyperlink: Full Text not Available

Journal: Journal of Geophysical Research: Space Physics

Title: Solar Modulation Parameter for Cosmic Rays Since 1936 Reconstructed from Ground-based Neutron Monitors and Ionization Chambers
General Information: Published 19 February 2011, Volume 116, Issue A2
Author(s): Ilya G. Usoskin, Galina A. Bazilevskaya, Gennady A. Kovaltsov
Abstract: The differential energy spectrum of galactic cosmic rays near Earth is often parameterized by the force field model with the only time-dependent parameter, the modulation potential ϕ. Here we present a series of reconstructed monthly values of the modulation potential for the period from July 1936 through December 2009. This works extends our earlier study by employing new data and improving the reconstruction method. The presented series is a composite of three parts. The most reliable part is based on data from the world network of sea level neutron monitors and covers the period since April 1964. The part between February 1951 and March 1964 is based on data from one to two mountain neutron monitors of IGY type and is characterized by larger uncertainties and possible systematic error. The part related to the period before 1951 is based on data from Forbush ground-based ionization chambers and is characterized by large uncertainties and should be taken with caveats. The reconstructed series has been tested against long-term data of balloon-borne measurements of flux of cosmic ray ionizing radiation in the stratosphere performed by the Lebedev Institute since 1957. The comparison shows good agreement since 1964 but suggests that the result before 1964 may contain larger errors in that the NM-based reconstruction method may underestimate the low energy part of GCR spectrum.

89) (2)

Journal: Bulletin of the Russian Academy of Sciences: Physics
Title: Efficiency of Detection for Neutron Detectors with Different Geometries
General Information: Published June 2011, Volume 75, Issue 6, Pages 866-868
Author(s): A. A. Abunin , E. V. Pletnikov, A. L. Shchepetov, V. G. Yanke
Abstract: The response of neutron detectors to the flux of secondary cosmic radiation particles incident on the detectors is simulated mathematically and detection efficiencies are found for neutron detectors of various designs.

90) (3)

Yu, Xiao Xia, et al. "Influence of Magnetic Clouds on Variations of Cosmic Rays in November 2004." Solar Physics 263.1-2 (2010): 223+. Academic OneFile. Web. 6 Jan. 2016.
Abstract: We investigate the effects of two magnetic clouds on hourly cosmic-ray intensity profiles in the Forbush decrease events in November 2004 observed by 47 ground-based neutron-monitor stations. By using a wavelet decomposition, the start time of the main phase in a Forbush decrease event can be defined, and then clearer definitions of initial phase, main phase, and recovery phase are proposed. Our analyses suggest that the main phase of this Fd event precedes the arrival time of the first magnetic cloud by about three hours, and the Fds observed at the majority (39/47) of the stations were found to originate from the sheath region as indicated by large fluctuations in magnetic field vectors at 19:00 UT on 7 November 2004, regardless of the station location. In addition, about 45% of the onset times of the recovery phase in the Forbush decreases took place at 04:00 UT on 10 November, independent of the station position. The results presented here support the hypothesis that the sheath region between the shock and the magnetic cloud, especially the enhanced turbulent magnetic field, results in the scattering of cosmic-ray particles, and causes the following Forbush decreases. Analysis of variation profiles from different neutron monitors reveals the global simultaneity of this Forbush decrease event. Moreover, we infer that the interplanetary disturbance was asymmetric when it reached the Earth, inclined to the southern hemisphere. These results provide several observational constraints for more detailed simulations of the Forbush decrease events with time-dependent cosmic-ray modulation models.

91) (1)

Journal: American Institute of Physics: Conference Proceedings
Title: Simultaneous Observation of Solar Neutrons and Effects on Terrestrial Magnetic Field in Association with a Solar Flare
General Information: Published online 30 April 2009
Author(s): Wara Chamani, Rolando Ticona, Edgar Ricaldi
On November 2, 2003 at 17:03:00 UT a solar flare, registered by the GOES satellite, was also recorded by the Neutron Monitor (NM64) of Cosmic Ray Laboratory at Mount Chacaltaya. This flare affected the local geomagnetic field (F): there were variations in the intensity of the horizontal component (H), declination component (D) and vertical component (Z). Variations on these components, estimated as 71 nT, 10 deg. and 19 nT, respectively, have been observed with the Patacamaya’s Geomagnetic Observatory; as well as a net increased field (F), estimated as 66 nT, recorded by the Villa Remedios Geomagnetic Observatory. The duration of the magnetic and neutron signals was approximately 40 and 54 minutes, respectively, which shows that the flare was intense and with large emission of neutrons.

92) (1)

Y. Muraki, Y. Matsubara, S. Masuda et al., “Detection of high-energy solar neutrons and protons by ground level detectors on April 15, 2001,” Astroparticle Physics, vol. 29, no. 4, pp. 229–242, 2008.
Abstract: In association with the large solar flare of April 15, 2001, the Chacaltaya neutron monitor observed a 3.6σ enhancement of the counting rate between 13:51 and 14:15 UT. Since the enhancement was observed beginning 11 min before the GLE, solar neutrons must be involved in this enhancement. The integral energy spectrum of solar neutrons can be expressed by a simple power law in energy with the index γ=-3.0±1.0. On the other hand, an integral energy spectrum of solar protons has been obtained in the energy range between 650 MeV and 12 GeV. The spectrum can also be expressed by a power law with the power index γ=-2.75±0.15. The flux of solar protons observed at Chacaltaya (at ⩾12 GeV) was already one order less than the flux of the galactic cosmic rays. It may be the first simultaneous observation of the energy spectra of both high-energy protons and neutrons. Comparing the Yohkoh soft X-ray telescope images with the observed particle time profiles, an interesting picture of the particle acceleration mechanism has been deduced.

93) (2)

Journal: American Institute of Physics: Conference Proceedings
Title: Solar Energetic Particle Intensities above the Streaming Limit
General Information: Published online 25 August 2008
Author(s): D. Lario, R. B. Decker, A. Aran
Abstract: Solar cycle 23 offered us several solar energetic particle (SEP) events with peak intensities measured early in the events that exceeded the previously determined streaming limit intensity. In the context of the theory that includes the effects that waves generated by energetic particles streaming along magnetic field lines have on the energetic particle transport itself, the mechanisms that allow us to explain the exceeding of the streaming limit during the prompt component of the SEP events include either the inhibition of wave amplification by the streaming particles and/or the existence of large‐scale interplanetary structures able to modify the SEP transport. We analyze these possibilities for the SEP events where either the 40–80 MeV or the 165–500 MeV proton intensities were observed in excess of the previously determined streaming limit by a factor of 4 or more.

94) (3)

Journal: Journal of Geophysical Research: Space Physics
Title: A Calibration Neutron Monitor: Energy Repsonse and Instrumental Temperature Sensitivity
General Information: Published 2 August 2008, Volume 113, Issue A8
Author(s): H. Kruger, H. Moraal, J. W. Bieber, J. M. Clem, P. A. Evenson, K. R. Pyle, M. L. Duldig, J. E. Humble
Abstract: Neutron monitors are integral detectors of secondary cosmic rays. Since each of them has its own detection efficiency, energy spectra cannot readily be derived from their observations. To circumvent this problem, latitudinal surveys have been conducted for many years with mobile neutron monitors to derive such spectra. Another way, however, is to use the worldwide stationary neutron monitor network, but then the counting rates of these monitors must be normalized sufficiently accurately against one another. For this reason, two portable calibration neutron monitors were built at the Potchefstroom campus of the North-West University, South Africa. When calibrations of an adequate number of the worldwide neutron monitors have been done, this paper demonstrates that the differential response functions derived from them will provide experimental data for modulation studies in the rigidity range of 1 to 15 GV. Several properties of these calibrators were investigated, in order to achieve sufficient calibration accuracy. The energy response over the cutoff rigidity range from the poles to the equator, as well as the instrumental temperature sensitivity, are described in this paper. The main conclusion is that the calibrator has a difference of almost 4% in its energy response over the cutoff rigidity range 0–16 GV in comparison with a standard 3NM64 neutron monitor. Furthermore, it is shown that not only the calibrator, but also the NM64 and IGY monitors, have fairly large instrumental temperature sensitivities. Correction coefficients for these effects are given.

95) (1)

Journal: Journal of Geophysical Research

Title: Long-Term Decline of South Pole Neutron Rates

General Information: Published 27 December 2007, Volume 112, Issue A12
Author(s): J. W. Bieber, J. Clem, D. Desilets, P. Evenson, D. Lal, C. Lopate, R. Pyle
Abstract: The count rate recorded by a neutron monitor at South Pole, Antarctica, displays a long-term decline over the 32-year span from 1965 to 1997. The neutron rate follows an 11-year cycle with maxima at times of low solar activity, but the 1997 peak rate was approximately 8% lower than the 1965 peak rate based on 27-d averages. This change is much larger than that recorded by any other neutron monitor. We suggest that the South Pole monitor, owing to its unique position at both high latitude and high altitude (2820 m), has enhanced sensitivity at 1–3 GV relative to a sea level monitor and may be responding to a change in the intensity of primary cosmic rays in this rigidity region. Measurements of cosmic rays made aboard stratospheric balloons and on the IMP-8 spacecraft support the possibility of a long-term change in cosmic ray intensity.

96) (2)

"Neutron events in the underground monitor of the Tien Shan high-altitude station." Bulletin of the Lebedev Physics Institute 34.4 (2007): 107+. Academic OneFile. Web. 6 Jan. 2016.
Abstract: The neutron multiplicity M spectrum was measured at the neutron monitor installed in the underground room of the Tien Shan high-altitude station (3340 m above sea level) of the Lebedev Physical Institute under a ground layer 20 m of water equivalent thick. To a first approximation, the differential multiplicity spectrum is power-law: dN/dM = 0.3 * [M.sup.-3.7[]m.sup.-2]s.sup.-1. The spectrum intensity is lower than the intensity of events in the ground-based NM64 supermonitor by a factor of 350--450. The spectrum slope exponent I3 + 1 = 3.7 +- 0.1 is identical to the exponent of the energy spectrum of bremsstrahlung gamma-rays of energetic muons (above 1 TeV) generated in a lead absorber of the monitor. In this case, the experimental intensity is hundred times higher than the expected intensity of events from muon bremsstrahlung. The spatial distribution of neutrons in the monitor suggests that they are produced by single particles. The temporal distribution of neutrons in the monitor is exponential with lifetime constant I = 360 - 390 Aus. Difficulties are indicated in the interpretation of the multiplicity spectrum by electromagnetic and nuclear interactions of muons in the monitor without involving new penetrating particles.
1   2   3   4   5   6   7

The database is protected by copyright © 2016
send message

    Main page