研究者詳細 - 塩川　和夫

論文 - 塩川　和夫

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Global imaging of polar cap patches with dual airglow imagers 査読有り

Hosokawa K., Taguchi S., Shiokawa K., Otsuka Y., Ogawa Y., Nicolls M.

GEOPHYSICAL RESEARCH LETTERS 41 巻 ( 1 ) 頁： 1 - 6 2014年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

During a 2 h interval from 2240 to 2440 UT on 12 November 2012, regions of increased 630.0 nm airglow emissions were simultaneously detected by dual all-sky imagers in the polar cap, one at Longyearbyen, Norway (78.1°N, 15.5°E) and the other at Resolute Bay, Canada (74.7°N, 265.1°E). The Resolute Bay incoherent scatter radar observed clear enhancements of the F region electron density up to 1012 m-3 within these airglow structures which indicates that these are optical manifestations of polar cap patches propagating across the polar cap. During this interval of simultaneous airglow imaging, the nightside/dawnside (dayside/duskside) half of the patches was captured by the imager at Longyearbyen (Resolute Bay). This unique situation enabled us to estimate the dawn-dusk extent of the patches to be around 1500 km, which was at least 60-70% of the width of the antisunward plasma stream seen in the Super Dual Auroral Radar Network convection maps. In contrast to the large extent in the dawn-dusk direction, the noon-midnight thickness of each patch was less than 500 km. These observations demonstrate that there exists a class of patches showing cigar-shaped structures. Such patches could be produced in a wide range of local time on the dayside nearly simultaneously and spread across many hours of local time soon after their generation. Key Points Image the entire shape of polar cap patches by combining dual airglow imagers Shape of the patches was much more elongated in the dawn-dusk direction Patches could be produced in a wide range of local time nearly simultaneously © 2013. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013GL058748

Web of Science

Scopus

Deducing Locations and Electrical properties of Lightning Discharges by ELF Network Observations in Japan 査読有り

Hobara Yasuhide, Hayaka Masashi, Shiokawa Kazuo

2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS) 頁： . 2014年

Latitudinal variation of stochastic properties of the geomagnetic field 査読有り

Wanliss J. A., Shiokawa K., Yumoto K.

NONLINEAR PROCESSES IN GEOPHYSICS 21 巻 ( 2 ) 頁： 347-356 2014年

Ground-Based Observations of Hiss-Like Emissions Changed from Chorus Emissions and Related Pulsating Aurora 査読有り

Ozaki M., Sawai K., Yagitani S., Shiokawa K., Miyoshi Y., Kataoka R., Ieda A., Ebihara Y., Katoh Y.

2014 XXXITH URSI GENERAL ASSEMBLY AND SCIENTIFIC SYMPOSIUM (URSI GASS) 2014年

Deducing locations and charge moment changes of lightning discharges by ELF network observations in Japan 査読有り

Hobara Y., Inoue T., Hayakawa M., Shiokawa K.

International Conference on Atmospheric Electricity, ICAE 2014 2014年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：International Conference on Atmospheric Electricity, ICAE 2014

Recent observations of electromagnetic radiations from lightning in the ELF frequency range so-called ELF transients are recognized as a powerful tool not only to deduce the global lightning distribution but also to obtain one of the most important properties of lightning discharges such as charge moment changes (CMCs). In this paper we demonstrate the spatio-temporal distributions of lightning discharges together with CMCs around Japan by using our newly developed domestic ELF observation network. This is the first time to obtain such type of distribution by using only ELF observations in the spatial scale of Japan (a few thousands km). We found that the obtained lightning source distributions both over the Pacific Ocean and the Sea of Japan are originated from the thunderstorm active regions confirmed by other measurements such as WWLLN. Statistical properties of the charge moment changes indicate that both number and CMC of positive CGs are superior to those of negative CGs. Moreover, considerably large CMC with both polarities are identified for the CGs over the Pacific Ocean as well as those with positive polarity over the Sea of Japan. Furthermore, we are going to present updated our lightning measurement network in Japan.

Scopus

Deducing locations and charge moment changes of lightning discharges by ELF network observations in Japan

Hobara Y., Inoue T., Hayakawa M., Shiokawa K.

IEEJ Transactions on Power and Energy 133 巻 ( 12 ) 頁： 994 - 1000 2013年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEJ Transactions on Power and Energy

The electromagnetic radiations from lightning discharges have been intensively studied for a long time in different frequency ranges. Recent observations of electromagnetic radiations from lightning in the ELF (extremely low frequency) frequency range so-called ELF transients are recognized as a powerful tool to obtain one of the most important properties of lightning discharges; the charge moment changes (Qds). In this paper we demonstrate the spatio-temporal distributions of lightning discharges together with their charge moment change (CMC) around Japan by using our newly developed domestic ELF observation network. This is the first time to obtain such type of distribution by using only ELF observations in the spatial scale of Japan (a few thousands km). We found that the obtained lightning source distributions both over the Pacific Ocean and the Sea of Japan are originated from the thunderstorm active regions confirmed by other measurements such as WWLLN. Statistical properties of the charge moment changes indicate that both number and CMC of positive CGs are superior to those of negative CGs. Moreover considerably large CMC with both polarities are identified for the CGs over the Pacific Ocean as well as those with positive polarity over the Sea of Japan. © 2013 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejpes.133.994

Scopus

CiNii Research

イオノゾンデおよびファブリ・ペロー干渉計によって観測された子午面熱圏風の比較査読有り

西岡未知, 丸山隆, 大塚雄一, 津川卓也, 石橋弘光, 塩川和夫, 石井守

南極資料 57 巻 ( 3 ) 頁： 357 - 368 2013年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：国立極地研究所

電離圏ダイナミクスに大きく寄与する熱圏風についての理解を深めるため,イオノゾンデの磁気共役点観測により推定された南北方向の熱圏風(推定熱圏風)と,ファブリ・ペロー干渉計(FPI)観測により直接測定された南北方向の熱圏風との相関を調べた.推定熱圏風は,磁気共役点における熱圏風は等しい(赤道横断風モードが卓越する)という仮定のもとで導出される.2 つの手法で観測された夜間の熱圏風を比較するのは本研究が初めてである.2010 年のチェンマイ(タイ)とコトタバン(インドネシア)のイオノゾンデとFPI データを比較した結果,両者はおおむね良い相関を示したが,相関が悪い日もあった.相関が悪い事例は,赤道から収束・発散する成分を無視できず,赤道横断風モードが卓越するという仮定が成立しないと解釈されるものである.また,2 つの手法で求めた熱圏風の相関を季節別に調べると,2-4 月に両者の相関が高い一方,5-7 月に両者の相関が低いことがわかった.

CiNii Research

Typhoon-induced concentric airglow structures in the mesopause region 査読有り

Suzuki S., Vadas S. L., Shiokawa K., Otsuka Y., Kawamura S., Murayama Y.

GEOPHYSICAL RESEARCH LETTERS 40 巻 ( 22 ) 頁： 5983 - 5987 2013年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

We present the first reported gravity wave patterns in the mesopause region caused by a typhoon in the troposphere. On 10 December 2002, concentric rings of gravity waves in OH airglow were observed simultaneously by all-sky imagers in the Optical Mesosphere and Thermosphere Imager system in Japan, located at Rikubetsu (43.5°N, 143.8°E), Shigaraki (34.9°N, 136.1°E), and Sata (31.0°N, 130.7°E). The airglow structures, which were well defined and formed a coherent wave pattern expanding concentrically, were identified over 8 h (2135-2947 LT). We estimate the horizontal wavelength, horizontal phase speed, and wave period as 34.5 km, 50.2 m s-1, and 11.5 min, respectively. Infrared cloud images from the Geostationary Meteorological Satellite show that the center of the rings estimated from the airglow data corresponds to a spiral band of Typhoon Pongsona (T0226). This unique event provides new insight into coupling between the lower and upper atmosphere. ©2013. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013GL058087

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Comparison of meridional thermospheric winds observed by ionosondes and Fabry-Perot interferometers 査読有り Open Access

Nishioka M., Maruyama T., Otsuka Y., Tsugawa T., Ishibashi H., Shiokawa K., Ishii M.

Antarctic Record 57 巻 ( 3 ) 頁： 357 - 368 2013年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Antarctic Record

To comprehend ionospheric-thermospheric coupling, one must understand the thermospheric wind system. However, measuring the thermospheric wind using a Fabry-Perot interferometer (FPI) is not an easy task. Because of this difficulty, some researchers have estimated meridional wind velocities using data obtained from a pair of ionosonde stations near the geomagnetic conjugate points, under the assumption that the meridional wind is the same at the two ionosonde stations (transequatorial mode wind). In this paper, we construct the first comparison of the estimated meridional wind velocities with meridional wind observed with FPIs. We analyzed data from the ionosondes and FPIs installed at Chiang Mai, Thailand, and Kototabang, Indonesia, from 2010. We found that the estimated and observed wind velocities were generally in good agreement on most nights, although on some nights, the wind velocities were different. The assumption that the meridional wind is equal anywhere between the two ionosonde stations would not be suitable for the days when the winds were not in good agreement. We also investigated the seasonal dependence of the correlation between the estimated and observed meridional winds. They were in good agreement from February to April and were not in good agreement from May to July. © 2013 National Institute of Polar Research.

DOI： 10.15094/00009710

Open Access

Scopus

Recent advances in equatorial, low- and mid-latitude aeronomy Preface 査読有り

Bhattacharyya Archana, Chau Jorge L., Denardini Clezio M., Hysell David L., Makela Jonathan J., Shiokawa Kazuo, Kudeki Erhan

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS 103 巻頁： 1 - 2 2013年10月

Observation of nighttime medium-scale travelling ionospheric disturbances by two 630-nm airglow imagers near the auroral zone 査読有り

Shiokawa K., Mori M., Otsuka Y., Oyama S., Nozawa S., Suzuki S., Connors M.

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS 103 巻頁： 184-194 2013年9月

Ionogram-based range-time displays for observing relationships between ionosonde satellite traces, spread F and drifting optical plasma depletions 査読有り

Lynn K. J. W., Otsuka Y., Shiokawa K.

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS 98 巻頁： 105-112 2013年6月

Planetary wave induced wind and airglow oscillations in the middle latitude MLT region 査読有り

Takahashi H., Shiokawa K., Egito F., Murayama Y., Kawamura S., Wrasse C. M.

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS 98 巻頁： 97 - 104 2013年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Atmospheric and Solar-Terrestrial Physics

Upper mesosphere airglow emissions and temperature observed at Rikubetsu (43.5°N,143.8°E) and mesospheric winds observed at Wakkanai (45.4°N,141.8°E), Japan, from January to December 2005 were used to analyze periodic oscillations of 2-16 days. During the January to March period and after September, both winds and airglow demonstrated clear 8-, 10- and 16-day oscillations. Downward phase progressions observed in the oscillations indicate that these are a signature of Rossby mode planetary waves. The 16-day wave was more evident in the zonal wind than the meridional. The 10-day wave was observed in January and March, on the basis of only a few cycles superposed on the 16-day wave. Airglow OI 557.7nm, O2 and OH(6,2) band emissions and O2 rotational temperature also showed significant amplitude of oscillation induced by the wave passages. For the 10-day wave, OI557.7nm showed an amplitude of oscillation equals to or more than 50% of the mean intensity level, O2 ~45% and OH ~25%. Large amplitudes of oscillation of the airglow during the passage of planetary waves suggest the possible vertical transport of atomic oxygen in addition to the density and temperature variations intrinsic to the wave events. © 2013 Elsevier Ltd.

DOI： 10.1016/j.jastp.2013.03.014

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Substorm onset and expansion phase intensification precursors seen in polar cap patches and arcs 査読有り

Nishimura Y., Lyons L. R., Shiokawa K., Angelopoulos V., Donovan E. F., Mende S. B.

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 118 巻 ( 5 ) 頁： 2034 - 2042 2013年5月

プラズマバブル発生に伴う全電子数変化率の緯度依存性

鈴木順也, 中田裕之, 鷹野敏明, 津川卓也, 斉藤昭則, 大塚雄一, 塩川和夫

大気電気学会誌 = / Society of Atmospheric Electricity of Japan 7 巻 ( 1 ) 頁： 60 - 61 2013年4月

Evidence of gravity wave ducting in the mesopause region from airglow network observations 査読有り

Suzuki S., Shiokawa K., Otsuka Y., Kawamura S., Murayama Y.

GEOPHYSICAL RESEARCH LETTERS 40 巻 ( 3 ) 頁： 601 - 605 2013年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

We present observational evidence of gravity wave ducting and show, for the first time, that the ducting occurs over large horizontal distances in the mesopause region. An optical network of four all-sky imagers in Japan identified two-dimensional patterns of small-scale gravity wave bands in OH airglow images on 13 June 2004. The wave signatures clearly showed northward propagation of more than 1800 km over a wide range of latitudes. The horizontal wavelength, horizontal phase speed, and wave period were estimated from the airglow data as 33.4 km, 42.8 m s<sup>-1</sup>, and 13.4 min, respectively. The wave structure lasted for the whole 5-h airglow observation period. Simultaneous MF radar wind data and TIMED/SABER measurements suggested that the wave was trapped and ducted at the airglow height. The ducting likely contributed to the remarkable coherence of the wave as it propagated northward. Key Points An airglow imaging network in Japan provides gravity wave ducting signatures Gravity wave bands appear over a horizontal extent of more than 1800 km Simultaneous winds and temperature are consistent with gravity wave ducting © 2012. American Geophysical Union. All Rights Reserved.

DOI： 10.1029/2012GL054605

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Scopus

Ground and satellite observations of low-latitude red auroras at the initial phase of magnetic storms 査読有り Open Access

Shiokawa, K; Miyoshi, Y; Brandt, PC; Evans, DS; Frey, HU; Goldstein, J; Yumoto, K

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 118 巻 ( 1 ) 頁： 256 - 270 2013年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Geophysical Research: Space Physics

We report ground and satellite observations of unique low-latitude red auroras that appear at the initial phase of geomagnetic storms. For two events on 21 October 2001, and 6 April 2000, the low-latitude red auroras appeared at ∼45° MLAT (L ∼ 2) ∼ 1.5 h after the storm sudden commencement in the postmidnight sector in Japan. Comprehensive satellite data were available for the former event. The energetic neutral atom images obtained by the Imager for Magnetopause-to-Aurora Global Exploration satellite show rapid enhancement of ring current hydrogen and oxygen fluxes at radial distances of ∼ 2-8 RE after the storm sudden commencement and associated with several storm-time substorms. The hydrogen ring-current enhancement occurred particularly in the postmidnight sector where the red aurora was observed. The timing of oxygen flux enhancement associated with a storm-time substorm coincided with the red aurora appearance. This rapid and significant enhancement of energetic neutral atom flux was also confirmed by energetic ion data obtained by the NOAA/POES-16 satellite. Extreme ultraviolet plasmaspheric images obtained by Magnetopause-to-Aurora Global Exploration indicate that the plasmapause was located at L = 2.3-2.5 in the postmidnight sector during the event, indicating that a spatial overlap occurs between the plasmasphere and the enhanced ring current ions at L ∼ 2. Based on these observations, we suggest that large energization of high-energy ring-current ions in the postmidnight inner magnetosphere caused the spatial overlap of these ring-current ions with the low-energy plasmaspheric plasmas at L ∼ 2, producing the low-latitude red auroras at the very beginning of the storms. ©2012. American Geophysical Union. All Rights Reserved.

DOI： 10.1029/2012JA018001

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Geomagnetic conjugate observations of plasma-sheet electrons by the FAST and THEMIS satellites 査読有り Open Access

Lee, S; Shiokawa, K; McFadden, JP; Seki, K

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 118 巻 ( 1 ) 頁： 132 - 145 2013年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Geophysical Research: Space Physics

We investigate pitch-angle distributions and spectral shapes of auroral electrons simultaneously observed during three conjunction events by the FAST satellite at altitudes of 2500-3500 km and by the THEMIS satellite in the plasma sheet at 7-13 RE. All three events were on the lower latitude of the auroral oval. Conjunction event 1 occurred at ~1914:45 UT on 10 April 2008. Electron spectra at energies of 0.1-3 keV are correlated well between the two satellites, while the precipitating electrons above 3 keV are missing at FAST. Event 2 occurred at 1255:26 UT on 26 April 2008. Electron spectra above 3 keV are correlated well between the two satellites. An additional broad spectral peak at energies of 0.1-0.5 keV was observed by FAST. Event 3 occurred at 0058:04 UT on 25 December 2008. Precipitating electrons of 0.5-5 keV obtained by FAST are correlated well with those of THEMIS-C, while a monoenergetic peak at 0.1-0.2 keV was observed only by FAST. For the three conjunction events, we conclude that high-energy precipitating auroral electrons observed by FAST directly come from the equatorial plasma sheet, while low-energy precipitating electrons may come from middle altitudes as a result of acceleration by static potential differences. For missing high-energy (>3 keV) electrons of event 1, we speculate that the pitch-angle scattering by waves occurs only at a limited energy range. ©2012. American Geophysical Union. All Rights Reserved.

DOI： 10.1029/2012JA017805

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GPS observations of medium-scale traveling ionospheric disturbances over Europe 査読有り

Otsuka Y., Suzuki K., Nakagawa S., Nishioka M., Shiokawa K., Tsugawa T.

ANNALES GEOPHYSICAE 31 巻 ( 2 ) 頁： 163 - 172 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Annales Geophysicae

Two-dimensional structures of medium-scale traveling ionospheric disturbances (MSTIDs) over Europe have been revealed, for the first time, by using maps of the total electron content (TEC) obtained from more than 800 GPS receivers of the European GPS receiver networks. From statistical analysis of the TEC maps obtained 2008, we have found that the observed MSTIDs can be categorized into two groups: daytime MSTID and nighttime MSTID. The daytime MSTID frequently occurs in winter. Its maximum occurrence rate in monthly and hourly bin exceeds 70% at lower latitudes over Europe, whereas it is approximately 45% at higher latitudes. Since most of the daytime MSTIDs propagate southward, we speculate that they could be caused by atmospheric gravity waves in the thermosphere. The nighttime MSTIDs also frequently occur in winter but most of them propagate southwestward, in a direction consistent with the theory that polarization electric fields play an important role in generating the nighttime MSTIDs. The nighttime MSTID occurrence rate shows distinct latitudinal difference: The maximum of the occurrence rate in monthly and hourly bin is approximately 50% at lower latitudes in Europe, whereas the nighttime MSTID was rarely observed at higher latitudes. We have performed model calculations of the plasma density perturbations caused by a gravity wave and an oscillating electric field to reproduce the daytime and nighttime MSTIDs, respectively. We find that TEC perturbations caused by gravity waves do not show dip angle dependencies, while those caused by the oscillating electric field have a larger amplitude at lower latitudes. These dip angle dependencies of the TEC perturbation amplitude could contribute to the latitudinal variation of the MSTID occurrence rate. Comparing with previous studies, we discuss the longitudinal difference of the nighttime MSTID occurrence rate, along with the E- and F-region coupling processes. The seasonal variation, of the nighttime MSTID occurrence rate in Europe, is not consistent with the theory that the longitudinal and seasonal variations of the nighttime MSTID occurrence could be attributed to those of the Es layer occurrence. © 2013 Author(s).

DOI： 10.5194/angeo-31-163-2013

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Stereoscopic determination of all-sky altitude map of aurora using two ground-based Nikon DSLR cameras 査読有り

Kataoka R., Miyoshi Y., Shigematsu K., Hampton D., Mori Y., Kubo T., Yamashita A., Tanaka M., Takahei T., Nakai T., Miyahara H., Shiokawa K.

ANNALES GEOPHYSICAE 31 巻 ( 9 ) 頁： 1543 - 1548 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Annales Geophysicae

A new stereoscopic measurement technique is developed to obtain an all-sky altitude map of aurora using two ground-based digital single-lens reflex (DSLR) cameras. Two identical full-color all-sky cameras were set with an 8 km separation across the Chatanika area in Alaska (Poker Flat Research Range and Aurora Borealis Lodge) to find localized emission height with the maximum correlation of the apparent patterns in the localized pixels applying a method of the geographical coordinate transform. It is found that a typical ray structure of discrete aurora shows the broad altitude distribution above 100 km, while a typical patchy structure of pulsating aurora shows the narrow altitude distribution of less than 100 km. Because of its portability and low cost of the DSLR camera systems, the new technique may open a unique opportunity not only for scientists but also for night-sky photographers to complementarily attend the aurora science to potentially form a dense observation network. © Author(s) 2013.

DOI： 10.5194/angeo-31-1543-2013

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