Drift Effects and the Cosmic Ray Density Gradient in a Solar Rotation Period: First Observation with the Global Muon Detector Network (GMDN)

Okazaki, Yasushi; Fushishita, A.; Narumi, T.; Kato, C.; Yasue, S.; Kuwabara, T.; Bieber, J. W.; Evenson, P. A.; Silva, M. R. Da; Lago, A. Dal; Schuch, Nelson Jorge; Fujii, Z.; Duldig, M. L.; Humble, J. E.; Sabbah, I.; Kóta, J.; Munakata, K.

doi:10.1086/588277

Cited by 50 publications

(66 citation statements)

References 25 publications

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“…It has been used for studying the directional anisotropy of high-energy cosmic ray intensity which often shows a dynamic variation when an interplanetary coronal mass ejection (ICME) accompanied by a strong shock approaches and arrives at the Earth (Okazaki et al 2008). It also has been used for studying the physical aspects of these interplanetary structures (Munakata et al 2005;Kuwabara et al 2009).…”

Section: The Global Muon Detector Network (Gmdn)mentioning

confidence: 99%

“…There are many methods of analyzing and removing the temperature effect from cosmic ray intensity observed by ground muon detectors. The simplest methods consist of the comparison of the cosmic ray intensity with: surface temperature changes, the variation of the altitude of maximum muon production (MMP), or the temperature variation at this altitude (Blackett 1938;Hess 1940;Duperier 1949;Trefall 1955a;French & Chasson 1959;Okazaki et al 2008;De Mendonça et al 2013). There are also methods that consider the temperature variation along the entire atmosphere through empirical or theoretical analyses (Sagisaka 1986;Dorman 2004;Berkova et al 2011;De Mendonça et al 2013).…”

Section: Introductionmentioning

confidence: 99%

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The Temperature Effect in Secondary Cosmic Rays (Muons) Observed at the Ground: Analysis of the Global Muon Detector Network Data

Mendonça

Braga

Echer

et al. 2016

ApJ

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The analysis of cosmic ray intensity variation seen by muon detectors at Earthʼs surface can help us to understand astrophysical, solar, interplanetary and geomagnetic phenomena. However, before comparing cosmic ray intensity variations with extraterrestrial phenomena, it is necessary to take into account atmospheric effects such as the temperature effect. In this work, we analyzed this effect on the Global Muon Detector Network (GMDN), which is composed of four ground-based detectors, two in the northern hemisphere and two in the southern hemisphere. In general, we found a higher temperature influence on detectors located in the northern hemisphere. Besides that, we noticed that the seasonal temperature variation observed at the ground and at the altitude of maximum muon production are in antiphase for all GMDN locations (low-latitude regions). In this way, contrary to what is expected in high-latitude regions, the ground muon intensity decrease occurring during summertime would be related to both parts of the temperature effect (the negative and the positive). We analyzed several methods to describe the temperature effect on cosmic ray intensity. We found that the mass weighted method is the one that best reproduces the seasonal cosmic ray variation observed by the GMDN detectors and allows the highest correlation with long-term variation of the cosmic ray intensity seen by neutron monitors.

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Section: The Global Muon Detector Network (Gmdn)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Temperature Effect in Secondary Cosmic Rays (Muons) Observed at the Ground: Analysis of the Global Muon Detector Network Data

Mendonça

Braga

Echer

et al. 2016

ApJ

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“…We calculate the daily mean ξ GEO(GG) z in T and A sectors from hourly data in the same manner as described in the section 2.1 for the GMDN data analysis. Okazaki et al (2008) [2] showed that the day-to-day variation of ξ GEO(GG) z followed well the variation of ξ GEO is partly due to the statistical error of the GG-component in equation (2.2), but it is also due to the contribution from the equatorial anisotropy contained in the GG-component. Figure 1 shows the average ξ GEO(GG) z in every month.…”

Section: Pos(icrc2015)056mentioning

confidence: 80%

“…Based on observations of the NSA which varies depending on the orientation of the Interplanetary Magnetic Field (IMF) around the Earth, it has been demonstrated that the GG-component can be used for deriving reliable sector polarity of the IMF which is defined as away (toward) when the IMF directs away from (toward) the Sun [11]. It is also reported that the NSA deduced from the GG-component is consistent with the anisotropy observed with the GMDN [2,12].…”

Section: Introductionmentioning

confidence: 75%

“…The detection areas of MDs, except one at Nagoya which has an area of 6 m x 6 m, have been enlarged in several steps and are currently 4 m x 4 m at Hobart, 4 m x 8 m at São Martinho da Serra and 5 m x 5 m at Kuwait, respectively. The GMDN has been continuously in operation, precisely observing the anisotropy on hourly basis [2,3]. The GMDN data are available on the internet for open access at a web page: http://cosray.shinshu-u.ac.jp/crest/DB/Public/Archives/GMDN.php.…”

Section: Introductionmentioning

confidence: 99%

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North-south anisotropy of galactic cosmic rays observed with the Global Muon Detector Network (GMDN)

Munakata¹

2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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We analyze the north-south anisotropy (NSA) of galactic cosmic rays observed with the GMDN on an hourly basis and compare with the anisotropy derived from the GG-component of a large multidirectional muon detector at Nagoya, Japan. The NSA is a component of the three dimensional anisotropy vector parallel to the Earth's rotation axis. We find a significant seasonal variation of the NSA from the GG-component indicating the influence of the anisotropy component in the ecliptic plane to the NSA. We calculate the average and standard deviation of daily mean NSAs in the "toward" (T) and "away" (A) IMF sectors separately in each Carrington Rotation between December 1993 and November 2014. It is confirmed that the temporal variations of the NSA observed with the GMDN and GG-component are consistent with each other, as reported earlier. We find the T-A separation between average NSAs in T and A sectors shows a long-term variation with minima (maxima) around the solar activity minima (maxima). The standard deviation in each rotation also shows a similar long-term variation, keeping the ratio of T-A separation to the standard deviation roughly constant thorough out an entire period of analysis. We discuss this in relation with the "success rate" which is introduced as a parameter indicating to what extent we can infer the IMF sector polarity from the sign of the observed NSA.

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Measurement and simulation of neutron monitor count rate dependence on surrounding structure

et al. 2015

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Neutron monitors are the premier instruments for precise measurements of time variations (e.g., of solar origin) in the galactic cosmic ray (GCR) flux in the range of ∼1–100 GeV. However, it has proven challenging to accurately determine the yield function (effective area) versus rigidity in order to relate a neutron monitor's count rate with those of other monitors worldwide and the underlying GCR spectrum. Monte Carlo simulations of the yield function have been developed, but there have been few opportunities to validate these observationally, especially regarding the particular environment surrounding each monitor. Here we have precisely measured the count rate of a calibration neutron monitor near the Princess Sirindhorn Neutron Monitor (PSNM) at Doi Inthanon, Thailand (18.59∘N, 98.49∘E, 2560 m altitude), which provides a basis for comparison with count rates of other neutron monitors worldwide that are similarly calibrated. We directly measured the effect of surrounding structure by operating the calibrator outside and inside the building. Using Monte Carlo simulations, we clarify differences in response of the calibrator and PSNM, as well as the calibrator outside and inside the building. The dependence of the calibrator count rate on surrounding structure can be attributed to its sensitivity to neutrons of 0.5–10 MeV and a shift of sensitivity to nucleons of higher energy when placed inside the building. Simulated calibrator to PSNM count rate ratios inside and outside agree with observations within a few percent, providing useful validation and improving confidence in our ability to model the yield function for a neutron monitor station.

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Drift Effects and the Cosmic Ray Density Gradient in a Solar Rotation Period: First Observation with the Global Muon Detector Network (GMDN)

Cited by 50 publications

References 25 publications

The Temperature Effect in Secondary Cosmic Rays (Muons) Observed at the Ground: Analysis of the Global Muon Detector Network Data

The Temperature Effect in Secondary Cosmic Rays (Muons) Observed at the Ground: Analysis of the Global Muon Detector Network Data

North-south anisotropy of galactic cosmic rays observed with the Global Muon Detector Network (GMDN)

Measurement and simulation of neutron monitor count rate dependence on surrounding structure

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