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論文

The Role of deposition of cosmogenic $$^{10}$$Be for the detectability of solar proton events

Schaar, K.*; Spiegl, T.*; Langematz, U.*; 佐藤 達彦; Mekhaldi, F.*; Kunze, M.*; 三宅 芙沙*; 余田 成男*

Journal of Geophysical Research; Atmospheres, 129(11), p.e2023JD040463_1 - e2023JD040463_28, 2024/06

 被引用回数:0 パーセンタイル:0.00(Meteorology & Atmospheric Sciences)

Using a climate model, the impact of Beryllium-10 from galactic cosmic rays on the detectability of solar proton events in ice cores was simulated. We show that sedimentation can be a major deposition mechanism for Beryllium-10, especially at high latitudes. We found that the season of the solar proton event and the phase of the 11-year solar cycle during the event have an impact on its detectability.

論文

Negative excursion of surface electric fields during gamma-ray glows in winter thunderstorms

和田 有希*; 鴨川 仁*; 久保 守*; 榎戸 輝揚*; 林 省吾*; 澤野 達也*; 米徳 大輔*; 土屋 晴文

Journal of Geophysical Research; Atmospheres, 128(21), p.e2023JD039354_1 - e2023JD039354_20, 2023/11

 被引用回数:0 パーセンタイル:0.00(Meteorology & Atmospheric Sciences)

During the 2020-2021 winter season, we detected 6 gamma-ray glows at Kanazawa University, Japan. Negative surface electric fields (E-fields) were observed by a field mill during all the glow cases. In five of the six cases, the maximum E-field reached $$-$$12 $$mathrm{kV m}^{-1}$$, and the E-field during the glow detection was the strongest in 3 hours before and after the detection time. Therefore, negative charges should have been dominant in the thunderclouds that produced the gamma-ray glows, and electrons were probably accelerated and multiplied by the E-fields between a predominantly negative charge layer and a localized positive charge layer below. In addition, we extracted 8 non-detection cases in the 2020-2021 winter season, in which surface E-fields were stronger than $$-$$12 $$mathrm{kV m}^{-1}$$. In 5 of the 8 cases, radar echoes were inadequately developed, suggesting insufficient charge accumulation. On the other hand, the remaining 3 cases had well-developed radar echoes, and there was no significant difference from the detection cases.

論文

Termination of downward-oriented gamma-ray glow by normal-polarity in-cloud discharge activity

和田 有希*; Wu, T.*; Wang, D.*; 榎戸 輝揚*; 中澤 知洋*; 森本 健志*; 中村 佳敬*; 篠田 太郎*; 土屋 晴文

Journal of Geophysical Research; Atmospheres, 128(15), p.e2023JD038606_1 - e2023JD038606_9, 2023/08

 被引用回数:1 パーセンタイル:26.21(Meteorology & Atmospheric Sciences)

A gamma-ray glow, a minute-lasting burst of high-energy photons from a thundercloud, was detected by ground-based apparatus at Kanazawa University, Japan, in a winter thunderstorm on 18 December 2018. The gamma-ray glow was quenched by a lightning flash within a brief time window of 40 ms. The lightning flash produced several low-frequency (LF) E-change pulses that were temporally coincident withthe termination of the gamma-ray glow, and that were located within 0.5 km from the observation site by the Fast Antenna Lightning Mapping Array. The LF pulses had the same polarity as a positive cloud-to-ground current and a normal-polarity in-cloud current. Since this polarity is against the upward electric field for producing the gamma-ray glow (accelerating electrons to the ground), we infer that the glow was terminated by a normal-polarity in-cloud discharge activity between a middle negative layer and an upper positive layer.

論文

Modeling the transport and deposition of $$^{10}$$Be produced by the strongest solar proton event during the holocene

Spiegl, T. C.*; 余田 成男*; Langematz, U.*; 佐藤 達彦; Chhin, R.*; 納多 哲史*; 三宅 芙沙*; 草野 完也*; Schaar, K.*; Kunze, M.*

Journal of Geophysical Research; Atmospheres, 127(13), p.e2021JD035658_1 - e2021JD035658_21, 2022/07

 被引用回数:5 パーセンタイル:50.15(Meteorology & Atmospheric Sciences)

巨大な太陽放射遷移ベントが発生すると、大量の宇宙放射線起因核種が大気圏内に生成され、それらは大気を循環ながら地表に沈着し、氷床や古木の年輪に取り込まれる。本研究では、西暦775年に発生した巨大な太陽放射線イベントの条件を模擬し、地質年代学のみならず、太陽物理学や気候モデリングの検証を実施した。その結果、イベントが発生した季節、大気循環における成層圏の役割、宇宙線起因核種の地表面分布に関する新たな知見を得た。本研究において、原子力機構は、太陽放射線被ばく線量警報システムWASAVIESの技術を活用し、イベント発生時の宇宙線起因核種の初期分布を推定した。

論文

Multiple gamma-ray glows and a downward TGF observed from nearby thunderclouds

久富 章平*; 中澤 知洋*; 和田 有希*; 辻 結菜*; 榎戸 輝揚*; 篠田 太郎*; 森本 健志*; 中村 佳敬*; 湯浅 孝行*; 土屋 晴文

Journal of Geophysical Research; Atmospheres, 126(18), p.e2021JD034543_1 - e2021JD034543_12, 2021/09

 被引用回数:16 パーセンタイル:74.16(Meteorology & Atmospheric Sciences)

Around 17:00 on January 12, 2020 (UTC), radiation detectors installed at two locations with a 1.35 km separation in Kanazawa City, Japan, captured a total of four gamma-ray enhancements. The first pair was simultaneously observed at the two locations at 17:03 and were abruptly terminated by a lightning discharge. The remaining two enhancements were also nearly simultaneously observed $$sim$$3 min later, and one of them was also terminated by another lightning discharge. At the last termination, a downward terrestrial gamma-ray flash and a negative energetic in-cloud pulse were observed. Both pairs were associated with thundercloud cells. In the first pair, simultaneous detection in two locations 1.35 km apart suggests either a gamma-ray glow emerged in-between and time variability of its intensity were directly observed or there were two (or more) gamma-ray glows in the cell which reached the two detectors coincidentally. In the latter pair, the peak time in the downwind detector was $$sim$$40 s later than that of the upwind detector. If the irradiation region moved with the cell, it would have taken $$sim$$110 s. The discrepancy suggests either the glow moved 2.5 times faster than the cell or there were two (or more) glows in the cell. Also, the fact that the thunderstorm cell hosting the latter glows experienced the lightning discharge $$sim$$3 min before suggests that the strong electric field in the cell can develop within a few minutes.

論文

Deposition and dispersion of radio-cesium released due to the Fukushima Nuclear accident, 2; Sensitivity to aerosol microphysical properties of Cs-bearing microparticles (CsMPs)

梶野 瑞王*; 足立 光司*; 五十嵐 康人*; 佐藤 志彦; 澤田 壮弘*; 関山 剛*; 財前 祐二*; 佐谷 茜*; 鶴田 治雄*; 森口 祐一*

Journal of Geophysical Research; Atmospheres, 126(1), p.e2020JD033460_1 - e2020JD033460_23, 2021/01

 被引用回数:13 パーセンタイル:68.27(Meteorology & Atmospheric Sciences)

The dispersion and deposition of radio-cesium ($$^{137}$$Cs) carried by the two types (type A and type B) of water-insoluble Cs-bearing solid microparticles (CsMPs) released due to the Fukushima nuclear accident were simulated for the first time. The presence of type B CsMPs (70-400 $$mu$$m found in soil and 1-5 $$mu$$m found in air), associated with the hydrogen explosion of Unit 1 in the afternoon of March 12, could partly explain the simulated underestimation of total deposition over land by assuming that 100% of the Cs carriers were water-soluble submicron particles (WSPs). Type A CsMPs (0.1-10 $$mu$$m), released from Units 2 or 3 in the midnight between March 14 and 15, travelled over the Kanto Plain, the most populated plain in Japan. Differences in the size distribution of type A CsMPs altered the surface air concentration over Kanto substantially, by up to more than one order of magnitude. The major deposition mechanisms varied among dry, wet, and fog depositions depending on the size distribution. The simulated activity fractions due to the CsMPs in the total deposition were compared to those observed in surface soil for the first time. The observations could be explained by the simulations for the locations under the influence of type B CsMPs. However, the simulations were substantially underestimated for the locations influenced by type A CsMPs. There could be more fractions of type A CsMPs emission in the source term and/or the simulated deposition rates of type A CsMPs were underestimated.

論文

Photonuclear reactions in lightning, 2; Comparison between observation and simulation model

和田 有希*; 榎戸 輝揚*; 中澤 知洋*; 湯浅 孝行*; 古田 禄大; 小高 裕和*; 牧島 一夫*; 土屋 晴文

Journal of Geophysical Research; Atmospheres, 125(20), p.e2020JD033194_1 - e2020JD033194_15, 2020/10

 被引用回数:2 パーセンタイル:7.97(Meteorology & Atmospheric Sciences)

During a winter thunderstorm on 6th February 2017 in Japan, photonuclear reactions such as $$^{14}$$N($$gamma,n$$)$$^{13}$$N were triggered by a downward terrestrial gamma-ray flash (TGF), as reported by Enoto et al. (2017). In the present paper, we compare the observation with a simulation model of downward TGFs and subsequent photonuclear reactions constructed by the first paper of the series and Wada, Enoto, Nakazawa, et al. (2019). The observation and model consist of three components: annihilation gamma rays from positrons produced by $$beta^+$$-decay nuclei, de-excitation gamma rays originating from neutron captures, and radiation doses by TGF photons. Each component of the observation is reproduced by the simulation model, and we constrain a relation between the number of avalanche electrons and their production altitude of the downward TGF. The constrains by three components match within an order of magnitude. The downward TGF is estimated to comprise $$(0.5-2.5) times$$ 10$$^{19}$$ avalanche electrons above 1 MeV produced at an altitude of 1.4-2.7 km. Despite differences in altitude, direction, and season, downward TGFs in winter thunderstorms are thought to have the same mechanism of electron acceleration and multiplication in lightning as TGFs observed by in-orbit satellites.

論文

Photonuclear reactions in lightning, 1; Verification and modeling of reaction and propagation processes

和田 有希*; 榎戸 輝揚*; 中澤 知洋*; 小高 裕和*; 古田 禄大; 土屋 晴文

Journal of Geophysical Research; Atmospheres, 125(20), p.e2020JD033193_1 - e2020JD033193_17, 2020/10

 被引用回数:3 パーセンタイル:12.78(Meteorology & Atmospheric Sciences)

We report simulation results of photonuclear reactions in the atmosphere triggered by a downward terrestrial gamma-ray flash in lightning. Possible channels of reactions in the atmosphere and their cross sections are verified with the ENDF/B-VII.1 library. Monte-Carlo simulations with two stages are then performed with the Geant4 framework. In the first stage, electrons following the relativistic runaway electron avalanche spectrum are produced in a mass model of the atmosphere, and production of photoneutrons and $$beta^{+}$$-decay nuclei is calculated based on the nuclear data library. In total 1$$times$$$$10^{13}$$ neutrons and 4$$times$$$$10^{12}$$ $$beta^{+}$$-decay nuclei are produced by $$10^{18}$$ energetic electrons above 1 MeV. In the second stage, propagation of the photoneutrons and positrons from the $$beta^{+}$$-decay nuclei in the previous stage is calculated. As a result, we model on-ground distributions of fluxes and energy spectra for neutrons, neutron-related gamma rays, and annihilation ones. The simulation model is to be compared with photonuclear events detected in low-charge-center winter thunderstorms.

論文

High peak-current lightning discharges associated with downward terrestrial gamma-ray flashes

和田 有希*; 榎戸 輝揚*; 中村 佳敬*; 森本 健志*; 佐藤 光輝*; 牛尾 知雄*; 中澤 知洋*; 湯浅 孝行*; 米徳 大輔*; 澤野 達也*; et al.

Journal of Geophysical Research; Atmospheres, 125(4), p.e2019JD031730_1 - e2019JD031730_11, 2020/02

 被引用回数:23 パーセンタイル:77.71(Meteorology & Atmospheric Sciences)

During 2017-2018 winter operation of the Gamma-Ray Observation of Winter Thunderclouds experiment in Japan, two downward terrestrial gamma-ray flashes (TGFs) that triggered atmospheric photonuclear reactions were detected. They took place during winter thunderstorms on 5 December 2017 and 9 January 2018 at Kanazawa, Ishikawa Prefecture, Japan. Each event coincided with an intracloud/intercloud discharge, which had a negative-polarity peak current higher than 150 kA. Their radio waveforms in the low-frequency band are categorized as a distinct lightning type called energetic in-cloud pulse (EIP). Negative-polarity EIPs have been previously suggested to be highly associated with downward TGFs, and the present observations provide evidence of the correlation between them for the first time. Furthermore, both of the downward TGFs followed gamma-ray glows, minute-lasting high-energy emissions from thunderclouds. It is suggested that the negative EIPs took place with downward propagating negative leaders or upward positive ones developed in highly electrified regions responsible for the gamma-ray glows.

論文

Analysis of the ozone reduction event over the southern tip of South America in November 2009

秋吉 英治*; 門脇 正尚; 中村 東奈*; 杉田 孝史*; 廣岡 俊彦*; 原田 やよい*; 水野 亮*

Journal of Geophysical Research; Atmospheres, 123(22), p.12523 - 12542, 2018/11

AA2018-0443.pdf:12.61MB

 被引用回数:1 パーセンタイル:2.54(Meteorology & Atmospheric Sciences)

2009年11月に南米大陸南端で3週間続くオゾン全量の減少が生じた。オゾン監視装置(Ozone Monitoring Instrument)によって観測されたオゾン全量及びERA-interim再解析データの解析から、極渦崩壊時に極渦が南米大陸側へ移動したことによって、このオゾン全量の減少が生じたことが示された。極渦の移動は、西経120-150度及び南緯50-60度の対流圏から南米大陸西及び南米大陸南端上空の成層圏への波フラックスの増加と関連しており、この波活動によって下部成層圏に大規模なジオポテンシャル高度の負偏差が生じた。また、2009年11月に南米大陸西の500hPaのジオポテンシャル高度からブロッキングが診断された。これらの結果は、2009年11月のブロッキング領域からの波の伝搬を介した南半球対流圏のブロッキングと、2009年11月の南米大陸南端で見られた数週間のオゾン全量の減少との関連を示唆している。さらに、1979-2015年の各年11月の南米大陸南端の南緯50-60度と西経65-75度を対象としたオゾン全量偏差及び力学場の解析から、2009年11月のオゾン全量の負偏差は1979-2015年の37年間で最大規模の負偏差であり、下部成層圏の大規模なジオポテンシャル高度の負偏差と関連付けられた。

論文

Model intercomparison of atmospheric $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

佐藤 陽祐*; 滝川 雅之*; 関山 剛*; 梶野 瑞王*; 寺田 宏明; 永井 晴康; 近藤 裕昭*; 打田 純也*; 五藤 大輔*; Qu$'e$lo, D.*; et al.

Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10

 被引用回数:45 パーセンタイル:85.33(Meteorology & Atmospheric Sciences)

福島第一原子力発電所事故により放出された$$^{137}$$Csの大気中の挙動を理解するため、大気拡散モデル相互比較が実施され、12モデルが参加した。モデルで考慮される過程に起因するモデル間の差異に焦点を当てた解析を行うため、全モデルで同じ気象場、水平分解能、及び放出源情報が使用された。モデルアンサンブルによる観測された大気中$$^{137}$$Cs濃度上昇イベントの捕捉率は40%であり、FMSは80を超えた。解析の結果、大気中$$^{137}$$Cs濃度上昇イベントの再現には気象場が最も重要な要素であり、気象場の再現性が高い場合のモデル間の差異は、沈着及び拡散過程に起因していることが分かった。また、沈着フラックスが小さいモデル及び拡散が強いモデルは高い性能を示したが、拡散が強いモデルは大気中$$^{137}$$Cs濃度を過大評価する傾向を示した。

論文

Atmospheric modeling of $$^{137}$$Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of Japan

北山 響*; 森野 悠*; 滝川 雅之*; 中島 映至*; 速水 洋*; 永井 晴康; 寺田 宏明; 斉藤 和雄*; 新堀 敏基*; 梶野 瑞王*; et al.

Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07

 被引用回数:26 パーセンタイル:68.70(Meteorology & Atmospheric Sciences)

日本学術会議のモデル相互比較プロジェクト(2014)で提供された、福島第一原子力発電所事故時に大気中に放出された$$^{137}$$Csの計算に用いられた7つの大気輸送モデルの結果を比較した。本研究では、東北及び関東地方に輸送された9つのプルームに着目し、モデル結果を1時間間隔の大気中$$^{137}$$Cs濃度観測値と比較することにより、モデルの性能を評価した。相互比較の結果は、$$^{137}$$Cs濃度の再現に関するモデル性能はモデル及びプルーム間で大きく異なることを示した。概してモデルは多数の観測地点を通過したプルームを良く再現した。モデル間の性能は、計算された風速場と使用された放出源情報と一貫性があった。また、積算$$^{137}$$Cs沈着量に関するモデル性能についても評価した。計算された$$^{137}$$Cs沈着量の高い場所は$$^{137}$$Csプルームの経路と一致していたが、大気中$$^{137}$$Cs濃度を最も良く再現したモデルは、沈着量を最も良く再現したモデルとは異なっていた。全モデルのアンサンブル平均は、$$^{137}$$Csの大気中濃度と沈着量をともに良く再現した。これは、多数モデルのアンサンブルは、より有効で一貫したモデル性能を有することを示唆している。

論文

Fogwater deposition modeling for terrestrial ecosystems; A Review of developments and measurements

堅田 元喜

Journal of Geophysical Research; Atmospheres, 119(13), p.8137 - 8159, 2014/07

 被引用回数:39 パーセンタイル:71.83(Meteorology & Atmospheric Sciences)

植生地への霧沈着モデリングに関するここ数十年間の進展をレビューする。霧沈着の推定のためのいくつかの種類のモデルと簡易パラメタリゼーションをその仮定・入力データ・モデル化したプロセスを比較しながら概観する。モデル計算から得られる霧沈着速度($$V$$$$_{rm d}$$)と植生種・構造との関係は、モデルの検証のために本研究で収集した文献と一致する。しかし、森林での$$V$$$$_{rm d}$$の観測値は複雑地形における観測の不確定性のために大きくばらついており、モデル計算値との定量的な比較は極めて困難である。文献調査によると、$$V$$$$_{rm d}$$の観測値は草地で2.1-8.0cm s$$^{-1}$$、森林で7.7-92cm s$$^{-1}$$であった。霧沈着が大気-陸面相互作用に及ぼす影響や複雑地形における霧沈着に関する数値的研究を紹介する。最終的に、更なる研究の進展に必要と考えられる新しいモデリングおよび観測手法を議論する。

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