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Journal Articles

Meteorological aspects of gamma-ray glows in winter thunderstorms

Wada, Yuki*; Enoto, Teruaki*; Kubo, Mamoru*; Nakazawa, Kazuhiro*; Shinoda, Taro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Yuasa, Takayuki*; Ushio, Tomoo*; Sato, Yosuke*; et al.

Geophysical Research Letters, 48(7), 11 Pages, 2021/04

 Times Cited Count:15 Percentile:93.45(Geosciences, Multidisciplinary)

During three winter seasons from November 2016 to March 2019, 11 gamma-ray glows were detected at a single observation site of our ground-based gamma-ray monitoring network in Kanazawa, Japan. These events are analyzed with observations of an X-band radar network, a ceilometer, a disdrometer, and a weather monitor. All the detected glows were connected to convective high-reflectivity regions of more than 35 dBZ, developed up to an altitude of $$>$$2 km. They were also accompanied by heavy precipitation of graupels. Therefore, graupels in the lower layer of thunderclouds that correspond to high-reflectivity regions can form strong electric fields producing gamma-ray glows. Also, these events are compared with a limited sample of nondetection cases, but no significant differences in meteorological conditions were found between detection and nondetection cases in the present study.

Journal Articles

Termination of electron acceleration in thundercloud by intracloud/intercloud discharge

Wada, Yuki*; Bowers, G. S.*; Enoto, Teruaki*; Kamogawa, Masashi*; Nakamura, Yoshitaka*; Morimoto, Takeshi*; Smith, D.*; Furuta, Yoshihiro*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; et al.

Geophysical Research Letters, 45(11), p.5700 - 5707, 2018/06

 Times Cited Count:23 Percentile:75.3(Geosciences, Multidisciplinary)

Journal Articles

Migrating source of energetic radiation generated by thunderstorm activity

Torii, Tatsuo; Sugita, Takeshi; Kamogawa, Masashi*; Watanabe, Yasuyuki*; Kusunoki, Kenichi*

Geophysical Research Letters, 38(24), p.L24801_1 - L24801_5, 2011/12

 Times Cited Count:58 Percentile:84.69(Geosciences, Multidisciplinary)

We identify a migrating source of high energy radiation, lasting for several minutes, attributed to thunderstorm activities through the observations of radiation, atmospheric electric field, and meteorological radar echoes at several points. Our findings indicate that the energetic radiation is emitted continuously from a downward hemispherical surface without lightning, the bottom of which is about 300 m above sea level, and this source of radiation moves from north to south above the observation site at a speed of about 7 m/s. The radiation source probably moves along with the negatively charged region of the cloud at the height of around 1 km, because the estimated migration of the radiation source is consistent with the observed movement of atmospheric electric field variation between ground-based observation sites and with the wind speed and direction at about 1 km altitude. This movement implies that the intensive electric field produced by the charged region in the thundercloud generates a radiation source. In addition, our results suggest that the low altitude of radiation source is related to no lightning activity during the energetic radiation emission.

Journal Articles

The Existence of memory effect on hydrogen ordering in ice; The Effect makes ice attractive

Arakawa, Masashi*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B.*; Fukazawa, Hiroshi

Geophysical Research Letters, 38, p.L16101_1 - L16101_5, 2011/08

 Times Cited Count:13 Percentile:37.43(Geosciences, Multidisciplinary)

The existence of ferroelectric ice XI with ordered hydrogen in space becomes of interest in astronomy and physical chemistry because of the strong electrostatic force. However, the influence was believed to be limited because it forms at narrow temperature range. From neutron diffraction experiments, we found that small hydrogen-ordered domains exist at significantly higher temperature and the domains induce the growth of "bulk" ice XI. The small ordered domain is named "memory" of hydrogen ordered ice because it is the residual structure of ice XI. Since the memory exists up to at least 111 K, most of ices in the solar system are hydrogen ordered and may have ferroelectricity. The small hydrogen-ordered domains govern the cosmochemical properties of ice and evolution of icy grains in the universe.

Journal Articles

Gradual increase of energetic radiation associated with thunderstorm activity at the top of Mt. Fuji

Torii, Tatsuo; Sugita, Takeshi*; Tanabe, Sachiko*; Kimura, Yoshihisa*; Kamogawa, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*

Geophysical Research Letters, 36(13), p.L13804_1 - L13804_4, 2009/07

 Times Cited Count:50 Percentile:78.09(Geosciences, Multidisciplinary)

Fluctuations of energetic radiation that seemed to be caused by a summer thunderstorm were observed at the top of Mt. Fuji. The largest of such fluctuations was gradual and lasted for about 20 minutes, and was found to be high-energy $$gamma$$ rays having a continuous energy spectrum up to 10 MeV or more. As for the feature of these fluctuations, it seems naturally that such fluctuations are caused by the bremsstrahlung photons generated by the energetic electrons produced continuously with an intense electric field in the thundercloud rather than originated in the process of lightning discharge.

Journal Articles

Iron in the Japan Sea and its implications for the physical processes in deep water

Takata, Hyoe*; Kuma, Kenshi*; Isoda, Yutaka*; Otosaka, Shigeyoshi; Senju, Tomoharu*; Minakawa, Masayuki*

Geophysical Research Letters, 35(2), p.L02606_1 - L02606_5, 2008/01

Concentrations of iron in seawater (dissolved and labile dissolved phases) in the two basins (Yamato Basin and Japan Basin) of the Japan Sea are measured and the origin and behavior of iron were discussed. Extremely high vertically integrated total dissolvable Fe inventories (300-350 $$mu$$mol m$$^{-2}$$) were observed at the surface water in both basins (0-200 m depth), and was probably resulting from high atmospheric Fe input to the surface water. Labile dissolved Fe in both basins was characterized by mid-depth (1-2 km depth) maxima, which were regulated by the competition between dissolved Fe input from the microbial decomposition of sinking biogenic organic matter and Fe removal by particulate scavenging. The distributions of Fe in the Japan Sea would play an important role in understanding the biogeochemical cycle of iron in the ocean.

Journal Articles

Relationship between helium isotopes and heat flux from hot springs in a non-volcanic region, Kii Peninsula, Southwest Japan

Umeda, Koji; Sakagawa, Yukihiro*; Ninomiya, Atsushi; Asamori, Koichi

Geophysical Research Letters, 34(5), p.L05310_1 - L05310_5, 2007/03

In order to examine the potential correlation between heat and helium isotope signatures in a non-volcanic region, we estimated the local heat flux using Peclet number analysis of thermal profile from deep boreholes in the Kii Peninsula, Southwest Japan. There is a distinct correlation between the common logarithms of $$^{3}$$He/$$^{4}$$He ratio and heat flux. Here heat flux values higher than 90 mW/m$$^{2}$$ are estimated from the deep boreholes and the upward flow of deep fluids predominates over the groundwater recharge of the local hydrology. These results support the recently proposed source model that shows that the high temperature hot springs with significantly higher $$^{3}$$He/$$^{4}$$He ratio in the Kii Peninsula originate due to the effective transfer of mantle helium and heat from the subcrustal lithosphere by aqueous fluids generated by dehydration of the subducting Philippine Sea slab.

Journal Articles

Variation of velocity and volume transport of the Tsugaru warm current in the winter of 1999-2000

Ito, Toshimichi; Togawa, Orihiko; Onishi, Mitsuyo*; Isoda, Yutaka*; Nakayama, Tomoharu*; Shima, Shigeki*; Kuroda, Hiroshi*; Iwahashi, Masayuki*; Sato, Chizuru*

Geophysical Research Letters, 30(13), p.11_1 - 11_4, 2003/10

The variation of velocity and volume transport of the Tsugaru Warm Current (TWC) is investigated based on the data of continuous and cross-sectional current monitoring in the Tsugaru Strait. During November 1999 - March 2000, the structure of the velocity transection across the strait was almost stable in which the TWC occupied the central part of the strait, while the returning flows existed in the northern and southern part of the strait, and these indicate a totally declining trend. The volume transport of the TWC varies from 2.1 to 1.1 Sv, with the mean value of 1.5 Sv, following the variation of the TWC. The temporal variation of the volume transport shows a linear correlation with that of the sea level difference between the Japan Sea and the Pacific Ocean. The contribution of the sea level difference to the volume transport is estimated to be roughly 70 %.

Journal Articles

Viscosity change and structural transition of molten Fe at 5 GPa

Terasaki, Hidenori*; Kato, Takumi*; Urakawa, Satoru*; Funakoshi, Kenichi*; Sato, Kiminori*; Suzuki, Akio*; Okada, Taku

Geophysical Research Letters, 29(8), p.68_1 - 68_3, 2002/05

The in situ viscosity measurements of the pure molten Fe under high pressures were made by falling sphere X-ray radiography method. Viscosity coefficients at about 2000 K were 15-24 mPa s at 2.7-5.0 GPa, and 4-9 mPa s at 5.0-7.0 GPa. Drastic decrease was found at around 5 GPa, at which stable solid phase below the melting temperatures change from delta (bcc) to gamma (fcc) phases. The observation indicates the possibility that the structural change in the molten Fe occurs in a narrow pressure interval (1 GPa) at the similar condition with the phase transformation in the solid.

Journal Articles

Renewal of the bottom water after the winter 2000-2001 may spin-up the thermohaline circulation in the Japan Sea

Senju, Tomoharu*; Aramaki, Takafumi; Otosaka, Shigeyoshi; Togawa, Orihiko; Danchenkov, M. A.*; Karasev, E.*; Volkov, Y. N.*

Geophysical Research Letters, 29(7), p.53_1 - 53_4, 2002/04

The newly formed bottom water in the Japan Sea was observed in the summer of 2001 after the severe winter 2000-2001. The new bottom water, which was observed in the northwestern Japan Sea, showed low temperature, high salinity, high dissolved oxygen and low nutrients concentration compared to the old bottom water. The distribution of the bottom water indicates that the deep convection occurred in the area of south off Vladivostok, not the northern Japan Sea, and then the bottom water was advected to the observation area from the convection region. The record of current meters suggests that the deep convection occurred in the early-February, because strong flows faster than 10 cms-1 appeared abruptly from mid-February 2001. This formation event may contribute not only the relaxation of the anoxic trend in the bottom layer but also the spin-up of the thermohaline circulation in the Japan Sea.

Journal Articles

Dense GPS Array Observations Across the Atotsugawa Fault, Central Japan

; Ando, Masataka; *; *

Geophysical Research Letters, 30(6), p.8012_1 - 8012_4, 2002/00

 Times Cited Count:17 Percentile:40.21(Geosciences, Multidisciplinary)


Journal Articles

The Okhotsk-Pacific seawater exchange in the viewpoint of vertical profiles of radiocarbon around the Bussol' Strait

Aramaki, Takafumi; Watanabe, Shuichi*; Kuji, Tomoyuki*; Wakatsuchi, Masaaki*

Geophysical Research Letters, 28(20), p.3971 - 3974, 2001/10

 Times Cited Count:14 Percentile:38.09(Geosciences, Multidisciplinary)

Vertical profiles for radiocarbon were described around the Bussol' Strait for the first time. The uniformity of radiocarbon concentration at 0-400 m depth in the Bussol' Strait was observed, and expected that diapycnal mixing occurs by tide between the sub-surface water around the Bussol' Strait and the surface water in the Bussol' Strait. The Okhotsk-Pacific cross-sections through the Bussol' Strait of radiocarbon concentration and density suggested the intermediate water in the Sea of Okhotsk has the role of the Okhotsk-Pacific water exchange, and the deep water between the Sea of Okhotsk and the Pacific Ocean is mixed well rapidly through the Bussol' Strait. Using estimation of bomb produced C-14 inventories in each water column, it was suggested the quantities of the Okhotsk-Pacific water exchange may be essentially small.

Journal Articles

${it In situ}$ observation of ilmenite-perovskite phase transition in MgSiO$$_{3}$$ using synchrotron radiation

Ono, Shigeaki*; Katsura, Tomoo*; Ito, Eiji*; Kanzaki, Masami*; Yoneda, Akira*; Walter, M.*; Urakawa, Satoru*; Utsumi, Wataru; Funakoshi, Kenichi*

Geophysical Research Letters, 28(5), p.835 - 838, 2001/03

 Times Cited Count:79 Percentile:86.73(Geosciences, Multidisciplinary)

no abstracts in English

Journal Articles

High-pressure phase transformation in CaMgSi$$_{2}$$O$$_{6}$$ and implications for origin of ultra-deep diamond inclusions

Irifune, Tetsuo*; Miyashita, Minoru*; Inoue, Toru*; Ando, Junichi*; Funakoshi, Kenichi*; Utsumi, Wataru

Geophysical Research Letters, 27(21), p.3541 - 3544, 2000/11

 Times Cited Count:35 Percentile:65.03(Geosciences, Multidisciplinary)

no abstracts in English

Journal Articles

Formation of metastable assemblages and mechanisms of the grain-size reduction in the postspinel transformation of Mg$$_{2}$$SiO$$_{4}$$

Kubo, Tomoaki*; Otani, Eiji*; Kato, Takumi*; Urakawa, Satoru*; Suzuki, Akio*; Kambe, Yuichi*; Funakoshi, Kenichi*; Utsumi, Wataru; Fujino, Kiyoshi*

Geophysical Research Letters, 27(6), p.807 - 810, 2000/03

 Times Cited Count:32 Percentile:62.28(Geosciences, Multidisciplinary)

no abstracts in English

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