Warning System for Aviation Exposure to Solar Energetic Particles (WASAVIES) | National Institute of Information and Communications Technology

Highlights

Develop a system to estimate radiation dose due to solar energetic particles in real-time
Possible dose estimation up to 100 km above a ground at anywhere in the Earth
Provide ICAO a mandatory information for cosmic ray radiation protection management of aircrews

A research group led by the National Institute of Information and Communications Technology (NICT), the Japan Atomic Energy Agency (JAEA), and the National Institute of Polar Research (NIPR) succeeded to develop a WArning System for AVIation Exposure to Solar energetic particles (WASAVIES), which can estimate radiation dose due to solar energetic particles in real-time just after the solar flare occurrence.

This system can estimate radiation dose up to 100 km above a ground at anywhere in the Earth and monitor aircrew radiation dose in real-time. This system enables to give information on the aircrew radiation dose as a space weather information used for aviation operation management.

NICT starts to provide information on HF communications, GNSS positioning, and radiation exposure as the only Asian center for the International Civil Aviation Organization (ICAO) space weather centers. The system will have been used as the mandatory information to operate the ICAO center.

Background

Figure 1: Example of radiation dose along flight route of Tokyo to New York.

Recently, needs of space weather information are getting higher in various fields. Especially, the International Civil Aviation Organization (ICAO) decided to use space weather information for civil aviation flight operation in 2011. NICT was elected as the only Asian center for the ICAO space weather center, and starts a service on November 7, 2019.

ICAO concerns an increasing radiation exposure by cosmic rays as well as a disruption of HF communication and increasing an error of GNSS measurement caused mainly by solar activities, therefore, ICAO requires information on radiation dose by cosmic rays as space weather information. Since cosmic ray exposure is recognized as occupational radiation exposure, radiation dose management of aircrews is required for the civil aviation companies. (Almost no increase of radiation dose is expected on the ground.)

In this situation, the research group has developed a warning system for aviation exposure to solar energetic particles aiming to offer information on radiation dose by cosmic rays.

The main components of radiations from space are galactic cosmic rays (GCR) which come from outside the solar system and solar energetic particles (SEP) which sporadically come from the Sun when large solar flares occur. Estimation of radiation dose by GCR is relatively easy because it is almost constant in the short time scale. So, the system to estimate GCR dose is already practical and has been used for radiation exposure management in the several civil aviation companies.

On the other hand, the real-time estimation of radiation dose by SEP had been difficult so far because SEP suddenly increases when a large solar flare occurs and quickly decrease during several hours.

Achievements

We developed real-time SEP radiation dose estimation system, named WASAVIES, which can estimate SEP radiation dose at anywhere in the Earth just after solar flare occasion triggered by real-time detection of a sudden increase of SEP.

Although SEP radiation dose estimation systems have developed in the other countries, these ones used each of only ground-based or satellite-based observation data. On the other hand, our system has achieved high estimation performance by using both ground- and satellite-based observations simultaneously, just after detecting a sudden increase of SEP.

Also, various physical processes can be reproduced by integrating several models developed by researchers with different background field, and high estimation accuracy of SEP radiation dose has been achieved.

This system enables real-time monitoring of SEP radiation dose, and it is expected that the system is used for a civil aviation operation such as rerouting or change of flight altitude as a mandatory information.

This study is a successful example of interdisciplinary research that has been achieved through collaboration among researchers in various fields such as space weather, solar physics, upper atmosphere, nuclear physics, and radiation protection.

Information on WASAVIES is available at https://wasavies.nict.go.jp/index_e.html.

Figure 2: World dose map estimated by WASAVIES at a past large solar energetic particle event.
White lines show flight routes, along which the WASAVIES can specifically estimate the radiation dose.

Future Prospects

WASAVIES will further evolve not only for real-time estimation but also to improve the accuracy of prediction of radiation dose up to end of the event. We will push forward the development of the system to apply radiation exposure management for astronauts of manned space missions such as the moon and planet explorations, which will be prosperous in the near future.

NICT strives to contribute to the safer air operation as to providing state-of-the-arts knowledges on space weather to ICAO.

Role of each organization

NICT: Development of SEP transport simulation. Development and operation of WASAVIES website.
JAEA: Development of air shower simulation. Integration of all simulations.
NIPR: Development of SEP transport in the magnetosphere.
Hiroshima Univ.: Development of real-time event detection algorithm.
Ibaraki College: Improvement of SEP transport simulation in magnetosphere.
Nagoya Univ.: Performance assessment of the system.

Article information

Title: Real-Time and Automatic Analysis Program for WASAVIES: Warning System for Aviation Exposure to Solar Energetic Particles

Journal: Space Weather, 16, 924-935 (2018)

URL: https://doi.org/10.1029/2018SW001873

Authors: Tatsuhiko Sato¹, Ryuho Kataoka^2,3, Daikou Shiota^4,5, Yûki Kubo⁴, Mamoru Ishii⁴, Hiroshi Yasuda⁶, Shoko Miyake⁷, In Chun Park⁵, Yoshizumi Miyoshi⁵

Affiliation: 1 JAEA, 2 NIPR, 3 Sokendai, 4 NICT, 5 Nagoya Univ., 6 Hiroshima Univ., 7 Ibaraki College

Title: Radiation Dose Nowcast for the Ground Level Enhancement on 10-11 September 2017

Journal: Space Weather, 16, 917-923 (2018)

URL: https://doi.org/10.1029/2018SW001874

Authors: Ryuho Kataoka^1,2, Tatsuhiko Sato³, Shoko Miyake⁴, Daikou Shiota^5,6, Yûki Kubo⁵

Affiliation: 1 NIPR, 2 Sokendai, 3 JAEA, 4 Ibaraki College, 5 NICT, 6 Nagoya Univ.

Appendix

WASAVIES

WASAVIES (WArning System for AVIation Exposure to Solar energetic particles) is a system which estimates radiation dose in real-time and issues alerts when a sudden increase of radiation dose is detected (See Figure 3). The system composed mainly of three numerical simulations.

① Solar energetic particle transport simulation in the interplanetary space: developed by NICT.

② Solar energetic particle transport simulation in the magnetosphere: developed by NIPR and Ibaraki college.

③ Atmospheric air shower simulation: developed by JAEA.

By integrating the simulations, SEP dose at aircraft altitude can be estimated. An algorithm to detect a sudden increase of SEP in real-time from the data of ground-based neutron monitors and GOES satellite was developed by Hiroshima university to operate the system in real-time. Performance assessment of the system by using previous event data was performed by Nagoya university. The results of the assessment showed accuracy of ±ten percent without SEP event, and ±several tens of percent with SEP event. The system can estimate cosmic ray radiation dose at anywhere in the Earth from 0 to 100 km above ground, and along specific aviation route (See Figure 1).

This work was supported by MEXT/JSPS KAKENHI Grant Numbers JP15H05813, JP15H05815, and JP16H01180.

WASAVIES website

Detailed information on WASAVIES can be available at WASAVIES website.

https://wasavies.nict.go.jp/index_e.html

Glossary

solar flare

Explosive phenomena on solar surface. Almost all solar flares occur at sunspot area. When a large solar flare occurs, sometimes not only electro-magnetic radiations such as radiowave, visible light, UV, and X-ray but also solar energetic particles are emitted. Occurrence frequency of solar flares depends strongly on solar activity, which periodically changes with around 11 years.

Solar X-ray flux obtained by GOES satellite.
Slight increase of radiation dose occurred during a solar flare on 10 September 2017 (UTC).

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cosmic rays

Cosmic rays from space are composed of galactic cosmic rays (GCR), which constantly come far from the solar system, and solar energetic particles (SEP), which sporadically come from the Sun when large solar flares occur. While GCR flux depends on 11 years solar activity, it does not change a short time scale such as several days or a week. On the other hand, SEP flux suddenly increases due to large solar flares and quickly decrease with time scale of several hours to a day. In the extreme case, SEP flux can achieve 100 to 1,000 times GCR flux. A main component of both GCR and SEP is a proton. When the protons penetrate the terrestrial atmosphere, the protons hit atoms or molecules in the atmosphere, and nuclear reactions occur to produce secondary cosmic rays such as neutrons, gamma rays, and muons. These secondary cosmic rays cause increases of radiation dose at aircraft altitude. Note that almost no increase of radiation dose is expected on the ground.

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neutron monitors

Equipment to detect the secondary neutrons, which are produced by nuclear reaction in the atmosphere. Many neutron monitors have been operating in the world, and the data have been opened to the public in real-time by internet.

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GOES satellite

Meteorological satellite at geostationary orbit launched by the US. GOES stands for Geostationary Operational Environmental Satellite. Various radiation monitors are onboard to detect a sudden increase of SEP. The data have been opened to the public in real-time by internet.

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