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Journal Articles

Nowcast and forecast of galactic cosmic ray (GCR) and solar energetic particle (SEP) fluxes in magnetosphere and ionosphere; Extension of WASAVIES to earth orbit

Sato, Tatsuhiko; Kataoka, Ryuho*; Shiota, Daiko*; Kubo, Yuki*; Ishii, Mamoru*; Yasuda, Hiroshi*; Miyake, Shoko*; Miyoshi, Yoshizumi*; Ueno, Haruka*; Nagamatsu, Aiko*

Journal of Space Weather and Space Climate (Internet), 9, p.A9_1 - A9_11, 2019/03

Real-time estimation of astronaut doses during solar particle events (SPE) is one of the most challenging tasks in cosmic-ray dosimetry. We therefore develop a new computational method that can nowcast the solar energetic particle (SEP) as well as galactic cosmic-ray (GCR) fluxes on any Earth orbit during a large SPE associating with ground level enhancement. It is an extended version of WArning System for AVIation Exposure to Solar Energetic Particle, WASAVIES. The extended version, called WASAVIES-EO, can calculate the GCR and SEP fluxes outside a satellite based on its two-line element data. Moreover, organ dose and dose-equivalent rates of astronauts in the International Space Station (ISS) can be estimated using the system, considering its shielding effect. The accuracy of WASAVIES-EO was validated based on the dose rates measured in ISS, as well as based on high-energy proton fluxes observed by POES satellites.

Journal Articles

Transient ionization of the mesosphere during auroral breakup; Arase satellite and ground-based conjugate observations at Syowa Station

Kataoka, Ryuho*; Nishiyama, Takanori*; Tanaka, Yoshimasa*; Kadokura, Akira*; Uchida, Herbert Akihito*; Ebihara, Yusuke*; Ejiri, Mitsumu*; Tomikawa, Yoshihiro*; Tsutsumi, Masaki*; Sato, Kaoru*; et al.

Earth, Planets and Space (Internet), 71, p.9_1 - 9_10, 2019/01

 Percentile:100(Geosciences, Multidisciplinary)

Transient ionization of the mesosphere was detected at around 65 km altitude during the isolated auroral expansion occurred at 2221-2226 UT on June 30, 2017. A general-purpose Monte Carlo particle transport code PHITS suggested that significant ionization is possible in the middle atmosphere due to auroral X-rays from the auroral electrons of $$<$$10 keV.

Journal Articles

Comparison of cosmic-ray environments on earth, moon, mars and in spacecraft using PHITS

Sato, Tatsuhiko; Nagamatsu, Aiko*; Ueno, Haruka*; Kataoka, Ryuho*; Miyake, Shoko*; Takeda, Kazuo*; Niita, Koji*

Radiation Protection Dosimetry, 180(1-4), p.146 - 149, 2018/08

 Times Cited Count:1 Percentile:38.14(Environmental Sciences)

Cosmic-ray dose rates spatially and temporally change very much. In this study, we compared the calculated cosmic-ray environments on the Earth, Moon, and Mars as well as inside spacecraft on low-earth orbit (LEO) and at interplanetary space. In the calculation, a galactic cosmic-ray model developed in DLR and trapped proton/electron models AP9/AE9 were used for determining the incident cosmic-ray fluxes, and the Particle and Heavy Ion Transport code System, PHITS, was employed for the cosmic-ray transport simulation in the Earth, Lunar, and Martian systems as well as spacecraft. The virtual International Space Station (ISS) model developed by JAXA was adopted as the representative of spacecraft in the PHITS simulation. This paper focuses on the comprehensive discussions on the difference of cosmic-ray environments and the effective methods of their shielding in various exposure situations.

Journal Articles

Radiation dose nowcast for the ground level enhancement on 10-11 September 2017

Kataoka, Ryuho*; Sato, Tatsuhiko; Miyake, Shoko*; Shiota, Daiko*; Kubo, Yuki*

Space Weather, 16(7), p.917 - 923, 2018/07

 Times Cited Count:8 Percentile:2.3(Astronomy & Astrophysics)

A ground level enhancement (GLE) event occurred on 10-11 September 2017, associated with X8.2 solar flare exploded at western limb. The magnitude of the GLE was not so large even at the peak, but the duration of the event was longer than average. We briefly report the results of our manually conducted nowcast using WASAVIES (Warning System of AViation Exposure to Solar energetic particles). The maximum radiation dose rate at 12 km flight altitude was estimated to be approximately 2 $$mu$$Sv/h, which is only one-third of the corresponding background dose rate due to the galactic cosmic-ray exposure. This result verified the safety of aircrews and passengers in aviation during this event.

Journal Articles

Real time and automatic analysis program for WASAVIES; Warning system for aviation exposure to solar energetic particles

Sato, Tatsuhiko; Kataoka, Ryuho*; Shiota, Daiko*; Kubo, Yuki*; Ishii, Mamoru*; Yasuda, Hiroshi*; Miyake, Shoko*; Park, I.*; Miyoshi, Yoshizumi*

Space Weather, 16(7), p.924 - 936, 2018/07

 Times Cited Count:4 Percentile:11.05(Astronomy & Astrophysics)

A physics-based warning system of aviation exposure to solar energetic particles, WASAVIES, is improved to be capable of real-time and automatic analysis. In the improved system, the count rates of several neutron monitors (NM) at the ground level, as well as the proton fluxes measured by the GOES satellite are continuously downloaded at intervals of 5 min and used for determining the model parameters. The performance of WASAVIES is examined by analyzing the three major GLE events of the 21st century. A web-interface of WASAVIES is also developed and will be released in the near future through the public server of NICT.

Journal Articles

Cosmic ray modulation and radiation dose of aircrews during the solar cycle 24/25

Miyake, Shoko*; Kataoka, Ryuho*; Sato, Tatsuhiko

Space Weather, 15(4), p.589 - 605, 2017/04

 Times Cited Count:6 Percentile:23.92(Astronomy & Astrophysics)

Weak solar activity and high cosmic-ray flux during the coming solar cycle are qualitatively anticipated by the recent observation that show the decline in the solar activity levels. We have quantitatively predicted the cosmic-ray modulation and resultant radiation exposure at flight altitude by using the time-dependent and three dimensional model of the cosmic-ray modulation. The database of airshower simulation performed by Particle and Heavy Ion Transport code System, PHITS, was employed in the prediction. Our predictions of the neutron monitor counting rate and the radiation dose of aircrews during the solar cycle 24/25 have some natures caused by the charge sign dependence of the cosmic-ray modulation, such as the flat-top profiles.

Journal Articles

Ionization of protoplanetary disks by galactic cosmic rays, solar protons, and supernova remnants

Kataoka, Ryuho*; Sato, Tatsuhiko

Geoscience Frontiers, 8(2), p.247 - 252, 2017/03

 Times Cited Count:1 Percentile:81.48(Geosciences, Multidisciplinary)

Estimation of the depth-dose profile of ionization in protoplanetary disks by galactic cosmic rays (GCRs), solar protons, and by supernova remnants is of great importance in the analysis of planet formation. We therefore calculated the profile using Particle and Heavy Ion Transport code System PHITS. The attenuation length of GCR ionization is updated as 118 g cm$$^{-2}$$, which is approximately 20% larger than the popular value. Hard and soft possible spectra of solar protons give 5% larger and 20% smaller attenuation lengths compared with those from standard GCR spectra, respectively. Further, all of the attenuation lengths become 10% larger in the compound gas of cosmic abundance, e.g. 128 g cm$$^{-2}$$ for GCRs, which can significantly affect the minimum estimate of the size of dead zones in protoplanetary disks.

Journal Articles

Radiation dose of aircrews during a solar proton event without ground-level enhancement

Kataoka, Ryuho*; Nakagawa, Yumi*; Sato, Tatsuhiko

Annales Geophysicae (Internet), 33(1), p.75 - 78, 2015/07

 Times Cited Count:6 Percentile:55.27(Astronomy & Astrophysics)

A significant enhancement of radiation dose is expected for aircrews during ground-level enhancement (GLE) events, while the possible radiation hazard remains open question during on-GLE solar energetic particle (SEP) events. Using a new air shower simulation driven by the proton flux data obtained from GOES satellites, we show the possibility of significant enhancement of the effective dose rate of up to 4.5 $$mu$$Sv/h$$^{-1}$$ at conventional flight altitude of 12 km during the largest SEP event which did not cause a GLE. As a result, new GOES-driven model is proposed to give the upper limit of the radiation dose in the stratosphere during non-GLE SEP events.

Journal Articles

Interplanetary particle transport simulation for warning system for aviation exposure to solar energetic particles

Kubo, Yuki*; Kataoka, Ryuho*; Sato, Tatsuhiko

Earth, Planets and Space (Internet), 67, p.117_1 - 117_13, 2015/07

 Times Cited Count:6 Percentile:55.27(Geosciences, Multidisciplinary)

One of the extreme space weather phenomena are solar energetic particles (SEPs). The huge SEP event causes a radiation dose enhancement to aircrews to be warned as soon as possible. To warn a radiation dose enhancement to aircrew, we have tried to develop warning system for radiation exposure to solar energetic particles. This article describes one component of the system, which calculates temporal evolution of SEP intensity and spectrum just outside the terrestrial magnetosphere.

Journal Articles

Air shower simulation for WASAVIES; Warning system for aviation exposure to solar energetic particles

Sato, Tatsuhiko; Kataoka, Ryuho*; Yasuda, Hiroshi*; Yashiro, Seiji*; Kuwabara, Takao*; Shiota, Daiko*; Kubo, Yuki*

Radiation Protection Dosimetry, 161(1-4), p.274 - 278, 2014/10

 Times Cited Count:16 Percentile:9.29(Environmental Sciences)

We applied our simulation technique to the analysis of air shower induced by mono-energetic protons and alpha particles, which are the dominant component of SEP. The results of the simulations were summarized in a database containing particle fluxes for each condition as a function of the atmospheric depth. This database was then incorporated into our developing Warning System of AVIation Exposure to SEP called WASAVIES. In this system, the aircrew doses due to SEP exposure are estimated within 6 hours after the flare onset, using the established database multiplied with the SEP fluxes incident to the earth. The MHD Cube model is employed in the determination of the incident SEP fluxes. The procedures for the air shower simulation together with some initial results of the aircrew dose calculations for past ground-level enhancement (GLE) events will be presented at the meeting.

Journal Articles

Radiation dose forecast of WASAVIES during ground-level enhancement

Kataoka, Ryuho*; Sato, Tatsuhiko; Kubo, Yuki*; Shiota, Daiko*; Kuwabara, Takao*; Yashiro, Seiji*; Yasuda, Hiroshi*

Space Weather, 12(6), p.380 - 386, 2014/06

 Times Cited Count:12 Percentile:39.36(Astronomy & Astrophysics)

Solar energetic particles (SEP) sometimes induce air shower that significantly increase the radiation dose at flight altitudes. In order to inform the situation of such a space radiation hazard to aircrews, a physics-based forward model is developed as WASAVIES (Warning System for Aviation Exposure to SEP) based on the focused transport equation and Monte Carlo particle transport simulation of the air shower. WASAVIES gives the fastest and simplest way to predict the time profile of dose rate during ground-level enhancements (GLEs).

Journal Articles

The Nebula Winter; The United view of the snowball Earth, mass extinctions, and explosive evolution in the late Neoproterozoic and Cambrian periods

Kataoka, Ryuho*; Ebisuzaki, Toshikazu*; Miyahara, Hiroko*; Nimura, Tokuhiro*; Tomida, Takayuki*; Sato, Tatsuhiko; Maruyama, Shigenori*

Gondwana Research, 25(3), p.1153 - 1163, 2014/04

 Times Cited Count:11 Percentile:41.23(Geosciences, Multidisciplinary)

We propose the Nebula Winter model to explain catastrophic events of the earth, such as mass extinctions and snowball earth events. Encounters with nebulae, such as supernova remnants and dark clouds in the galaxy, can lead to a catastrophic environmental change on the Earth through the destruction of the ozone layer and climate forcing by enhanced fluxes of cosmic rays and cosmic dust particles.

Journal Articles

Predicting radiation dose aircraft from solar energetic particles

Kataoka, Ryuho*; Sato, Tatsuhiko; Yasuda, Hiroshi*

Space Weather, 9(8), p.S08004_1 - S08004_2, 2011/08

 Times Cited Count:11 Percentile:54.07(Astronomy & Astrophysics)

We held a half day session entitled "Predicting radiation dose from solar energetic particles" in the Japan Geoscience Union 2011 Meeting on 24 May 2011, in response to increasing public interest for space radiation dose during the ascending phase of the solar cycle 24. This is the first session in Japan to discuss the fundamental problems to predict the aviation radiation dose from SEP, provides a unique start point of an interdisciplinary approach.

Journal Articles

Explosive volcanic eruptions triggered by cosmic rays; Volcano as a bubble chamber

Ebisuzaki, Toshikazu*; Miyahara, Hiroko*; Kataoka, Ryuho*; Sato, Tatsuhiko; Ishimine, Yasuhiro*

Gondwana Research, 19(4), p.1054 - 1061, 2011/06

 Times Cited Count:5 Percentile:75.81(Geosciences, Multidisciplinary)

We examined the timing of 11 eruptive events that produced silica-rich magma from four volcanoes in Japan (Mt. Fuji, Mt. Usu, Myojin-sho, and Satsuma-Iwo-jima) over the past 306 years (from AD 1700 to AD 2005). Nine of the 11 events occurred during inactive phases of solar magnetic activity (solar minimum), which is well indexed by the group sunspot number. This strong association between eruption timing and the solar minimum is statistically significant to a confidence level of 96.7%. This relationship is not observed for eruptions from volcanoes with relatively silica-poor magma, such as Izu-Ohshima.

Oral presentation

Analytical model for calculating GCR spectra in the atmosphere PARMA/EXPACS and its future application to SEP

Sato, Tatsuhiko; Kataoka, Ryuho*; Yasuda, Hiroshi*

no journal, , 

The details of the analytical model for calculating GCR spectra in the atmosphere PARMA/EXPACS and its future application to the SEP research will be discussed in the presentation.

Oral presentation

Simulation of air shower induced by solar energetic particle

Sato, Tatsuhiko; Yasuda, Hiroshi*; Kataoka, Ryuho*; Yashiro, Seiji*; Kuwabara, Takao*; Shiota, Daiko*

no journal, , 

In order to precisely estimate the aircrew doses, the Monte Carlo simulation for air shower is indispensable. We had therefore simulated air showers induced by GCR, using a general-purpose Monte Carlo particle and heavy ion transport simulation code system PHITS, and established a model for calculating the aircrew doses anywhere in the world at the solar quiet time. In this study, we applied our simulation technique to the analysis of air shower induced by SEP, and established a model for estimating the aircrew doses from a given SEP energy spectrum and cutoff latitude. The model is to be incorporated into our developing Warning System of AVIation Exposure to SEP called WASAVIES.

Oral presentation

Space weather hazards on aviation exposure

Sato, Tatsuhiko; Kataoka, Ryuho*; Yasuda, Hiroshi*; Yashiro, Seiji*; Kuwabara, Takao*; Shiota, Daiko*

no journal, , 

We are trying to develop a two-step forecast system for the SEP doses named WASAVIES (WArning System of AVIation Exposure to SEP). The present status of the development of WASAVIES will be reported at the meeting, together with a brief summary of the currently operating systems for estimating the GCR and SEP doses.

Oral presentation

Verification of air shower simulation induced by solar energetic particles

Sato, Tatsuhiko; Yasuda, Hiroshi*; Kataoka, Ryuho*; Yashiro, Seiji*; Kuwabara, Takao*; Shiota, Daiko*

no journal, , 

When solar energetic particles (SEP) are incident to the atmosphere, they can induce air showers by generating varieties of secondary particles. Such secondary particles can reach conventional flight altitudes (12 km), and hence, aircrews are exposed to enhanced level of radiations. In order to precisely estimate the aircrew doses, the Monte Carlo simulation for air shower is indispensable. We therefore simulated air showers induced by mono-energetic protons, using a general-purpose Monte Carlo particle and heavy ion transport simulation code system PHITS, and developed a database of particle fluxes in the atmosphere. Combining the database with the proton fluxes measured by PAMELA during the GLE event occurred on Dec. 13th 2006, the count rates of the neutron monitor located at Thule were calculated. The calculated count rates agree with the measured data fairly well, verifying the accuracy of our simulation technique.

Oral presentation

Development of WASAVIES (Warning System of AVIation Exposure to SEP); System overview

Sato, Tatsuhiko; Yasuda, Hiroshi*; Kataoka, Ryuho*; Yashiro, Seiji*; Kuwabara, Takao*; Shiota, Daiko*; Kubo, Yuki*

no journal, , 

When solar energetic particles (SEP) are incident to the atmosphere, they can induce air showers by generating varieties of secondary particles. Such secondary particles can reach the deep into the atmosphere, and enhance the level of radiation doses. This can be a hazard of aircrews. In order to precisely estimate the radiation doses during large solar particle events, we are developing a warning system of aviation exposure to SEP, WASAVIES. The WASAVIES has been tested and verified by making a comparison between the measured and calculated count rates of several neutron monitors during past GLE (ground level enhancement) events. The final goal of our project is to predict the enhancement of radiation doses due to SEP exposure within 6 hours from the GLE onset.

Oral presentation

Estimation of astronaut dose inside the Kibo module during large solar flare events

Sato, Tatsuhiko; Kataoka, Ryuho*; Nagamatsu, Aiko*

no journal, , 

Forecast of radiation doses for astronauts as well as aircrews due to the exposure to solar energetic particles (SEP) is one of the greatest challenges in space weather research. In last 3 years, we have developed a warning system of aviation exposure to solar energetic particles: WASAVIES, which can predict the SEP doses at any flight conditions within 2.5 hours after the onset of ground level enhancements (GLE). In this system, the SEP fluxes incident to the atmosphere are calculated by physics based models, and they are converted to radiation doses using a database developed on the basis of air-shower simulation. In this study, we applied the same physics-based models to the estimate of the SEP fluxes on the orbit of International Space Station, and converted the fluxes to radiation doses for astronauts staying inside the Kibo module.

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