Neutron count rate

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Muon count rate

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※Data Information
This data is for a quick look and is subject to change or correction in the future. Use of this data for research planning and other purposes is at your own risk. Also, please contact us when you use the data.




The solar maximum is the peak of so-called 11-year sunspot cycles. From the 1980s, the sunspot number at the solar maxima gradually decreased. Zero sunspot days continued in the previous solar minimum in 2009, and the cosmic ray intensity was the largest in the observation history since 1950.

The purpose of this study is to evaluate the increase of the cosmic rays during the next solar minimum expected in 2020, and to understand the transient modulation of cosmic rays during solar flares.

There are two types of cosmic rays, i.e. muons and neutrons, which can be measured at ground. The current network observations of GMDN (Global Muon Detector Network) and SSE (Spaceship Earth) have independently achieved scientific goals. Combining both GMDN (muons) and SEE (neutrons) can open new science of space weather studies.

About cosmic ray observation at Syowa Station:

In 2018, we started new cosmic ray observation of both muons and neutrons at Syowa Station.

In middle latitudes, cosmic rays move across the magnetic field a lot before entering to the detectors, and we cannot distinguish whether the observed difference is due to the deflection or pure intensity variation.

In high-latitude, at Syowa Station, cosmic rays move across the magnetic field less, and we can measure the cosmic rays coming from the similar directions at two different energies. Also, the similar paths of cosmic rays allow us to investigate the dependence on atmospheric and geomagnetic activities better.

■About count rate

A total of six tubes of neutron monitors are installed at Showa Station. The value provided in this website is a 10-minute value as calculated by the average of six tubes, so that we use the data even if one or two tubes fail to observe. Strictly speaking, the middle tube have counts slightly higher than the others, so the base line may shift by the average.

The muon detector at Showa Base consists of 60 proportional counters (2 m tubes x20 and 1 m tubes x40). One meter tubes x20 are placed at right angles to 2 m tubes x10 to identify the incident position of the muon, and the direction of the muon's incidence is determined by placing two layers of these at the top and bottom. The data provided are the count rates (10-minute values) that are judged as vertical incident.

Neutron monitor
Muon monitor

Project Members

Chihiro Kato, Shinshu University

Ryuho Kataoka, National Institute of Polar Research

Akira Kadokura, ROIS-DS Polar Environment Data Science Center

Kazuoki Munakata, Shinshu University

Akiko Miyake, National Institute of Technology(KOSEN), Ibaraki College

Ayumu Kihara (Shinshi University), Kino Takasode (Shinshi University), Kiyoka Murase (Sokendai), Herbert Akihito Uchida (Sokendai)