A Peculiar ICME Event in August 2018 Observed With the Global Muon Detector Network

Kihara, W.; Munakata, K.; Kato, C.; Kataoka, Ryuho; Kadokura, Akira; Miyake, Shoko; Kozai, M.; Kuwabara, T.; Tokumaru, M.; Mendonça, R. R. S.; Echer, E.; Lago, A. Dal; Rockenbach, M.; Schuch, Nelson Jorge; Bageston, José Valentin; Braga, Carlos Roberto; Jassar, H. K. Al; Sharma, Madan Mohan; Duldig, M. L.; Humble, J. E.; Evenson, P. A.; Sabbah, I.; Kóta, J.

doi:10.1029/2020sw002531

Cited by 9 publications

(6 citation statements)

References 45 publications

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“…By analyzing the GMDN data recorded during this event, we found that a significant increase of the GCR density (omnidiectional intensity) exceeding the unmodulated level before the shock was observed for 6 h between 04:00 and 09:00 on 26 August, near the trailing edge of the MFR. Significant north directed anisotropy was also found during the same 6 h (Kihara et al, 2021). Although it is out of scope of this paper to describe our analysis of this event, observed by the GMDN in detail, we show how the data recorded by Syowa NM and MD are consistent with the observation by the GMDN.…”

Section: Preliminary Observations and Data Analysissupporting

confidence: 67%

New cosmic ray observations at Syowa Station in the Antarctic for space weather study

Kato¹,

Kihara²,

Ko³

et al. 2021

J. Space Weather Space Clim.

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Muon detectors and neutron monitors were recently installed at Syowa Station, in the Antarctic, to observe different types of secondary particles resulting from cosmic ray interactions simultaneously from the same location. Continuing observations will give new insight into the response of muon detectors to atmospheric and geomagnetic effects. Operation began in February, 2018 and the system has been stable with a duty-cycle exceeding 94%. Muon data shows a clear seasonal variation, which is expected from the atmospheric temperature effect. We verified successful operation by showing that the muon and neutron data are consistent with those from other locations by comparing intensity variations during a space weather event. We have established a web page to make real time data available with interactive graphics (http://polaris.nipr.ac.jp/cosmicrays/).

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Section: Preliminary Observations and Data Analysissupporting

confidence: 67%

New cosmic ray observations at Syowa Station in the Antarctic for space weather study

Kato¹,

Kihara²,

Ko³

et al. 2021

J. Space Weather Space Clim.

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“…We finally note a significant softening of the first-order anisotropy in the MFR period as indicated by γ 1 (blue curve in Figure 3(d)). So far γ 1 ∼ 0 has been assumed in analyses of the anisotropy observed by GMDN (e.g., Kihara et al 2020) based on the diffusive GCR transport picture in which the first-order anisotropy is expressed in terms of the diffusion balancing with the rigidity independent solar wind convection. However, γ 1 in Figure 3(d) might be indicating that the diffusive transport picture is not appropriate in the MFR period of this event.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…While most of the preceding studies using the NM network and GMDN separately have been limited to analyze the variations of the GCR density and the first-order anisotropy (Belov et al 2018;Tortermpun et al 2018;Kihara et al 2020), the second-order anisotropy also has a significant contribution to the GCR variation in some events. Bidirectional streaming (BDS) is often observed in satellite measurements of lowenergy electrons and ions indicating particles trapped in the MFR in which the field line is anchored on Sun at both ends.…”

Section: Introductionmentioning

confidence: 99%

Large-amplitude Bidirectional Anisotropy of Cosmic-Ray Intensity Observed with Worldwide Networks of Ground-based Neutron Monitors and Muon Detectors in 2021 November

Munakata

Kozai

Kato

et al. 2022

ApJ

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We analyze the cosmic-ray variations during a significant Forbush decrease observed with worldwide networks of ground-based neutron monitors and muon detectors during 2021 November 3–5. Utilizing the difference between primary cosmic-ray rigidities monitored by neutron monitors and muon detectors, we deduce the rigidity spectra of the cosmic-ray density (or omnidirectional intensity) and the first- and second-order anisotropies separately for each hour of data. A clear two-step decrease is seen in the cosmic-ray density with the first ∼2% decrease after the interplanetary shock arrival followed by the second ∼5% decrease inside the magnetic flux rope (MFR) at 15 GV. Most strikingly, a large bidirectional streaming along the magnetic field is observed in the MFR with a peak amplitude of ∼5% at 15 GV, which is comparable to the total density decrease inside the MFR. The bidirectional streaming could be explained by adiabatic deceleration and/or focusing in the expanding MFR, which have stronger effects for pitch angles near 90°, or by selective entry of GCRs along a leg of the MFR. The peak anisotropy and density depression in the flux rope both decrease with increasing rigidity. The spectra vary dynamically, indicating that the temporal variations of density and anisotropy appear different in neutron monitor and muon detector data.

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“…for the whole solar magnetic cycle, also considering high energy GCRs, especially the from Princess Sirindhorn Neutron Monitor, with vertical cut-off rigidity 16.8 GV (e.g. Deeprom and Nutaro, 2017) and muon telescopes from the Global Muon Detector Network (Kihara et al, 2021). We will continue to test the structure-function and detrended-fluctuationanalysis methods, focusing on the influence of different trend-removal techniques (Kantelhardt et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

Scaling Features of Diurnal Variation of Galactic Cosmic Rays

et al. 2021

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We analyze the scaling properties of the diurnal variation of galactic cosmic rays (GCRs) in Solar Cycle 24 and the solar minima between Solar Cycles 23/24 and 24/25 for 2007 – 2019 based on the count rates of the Oulu, Newark, Hermanus, and Potchefstroom neutron monitors. The scaling features of the GCR diurnal variation are studied by evaluating the Hurst exponent, a quantitative parameter used as an indicator of the state of the randomness of a time series. We estimate the Hurst exponents for GCR diurnal-variation parameters amplitude and phase using structure-function and detrended-fluctuation-analysis methods. Results show that the Hurst exponents for the GCR diurnal variation vary in the range from $\approx0.3$ ≈ 0.3 to $\approx0.9$ ≈ 0.9 , with a general tendency of being systematically above 0.5. It suggests that the GCR diurnal variation reveals a more persistent structure than Brownian motion. However, the time series of GCR diurnal-variation amplitude and phase evolve from a more persistent structure in the solar minimum between Solar Cycles 23/24 in 2007 – 2009 to a more random character in and near the solar maximum 2012 – 2014. This observation seems to be in agreement with the general configuration of the heliosphere through the 11-year solar-activity cycle. Moreover, the temporal profile of the Hurst exponent for GCR diurnal amplitude and phase around the beginning of the solar minimum between Solar Cycles 24/25 (2018 – 2019) differs from the solar minimum between Solar Cycles 23/24 in 2007 – 2009, suggesting a dependence on solar-magnetic polarity. These findings could shed more light on GCR particle transport in the turbulent heliosphere over the solar cycle.

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A Peculiar ICME Event in August 2018 Observed With the Global Muon Detector Network

Cited by 9 publications

References 45 publications

New cosmic ray observations at Syowa Station in the Antarctic for space weather study

New cosmic ray observations at Syowa Station in the Antarctic for space weather study

Large-amplitude Bidirectional Anisotropy of Cosmic-Ray Intensity Observed with Worldwide Networks of Ground-based Neutron Monitors and Muon Detectors in 2021 November

Scaling Features of Diurnal Variation of Galactic Cosmic Rays

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