Faculty Profiles - SHIOKAWA, Kazuo

Papers - SHIOKAWA, Kazuo

Division display 221 - 240 of about 483 ／ All the affair displays >>

Global imaging of polar cap patches with dual airglow imagers Reviewed

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

GEOPHYSICAL RESEARCH LETTERS Vol. 41 ( 1 ) page： 1 - 6 2014.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

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 degrees N, 15.5 degrees E) and the other at Resolute Bay, Canada (74.7 degrees N, 265.1 degrees E). The Resolute Bay incoherent scatter radar observed clear enhancements of the F region electron density up to 10(12) 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.

DOI： 10.1002/2013GL058748

Web of Science

Scopus

Deducing Locations and Electrical properties of Lightning Discharges by ELF Network Observations in Japan Reviewed

Hobara Yasuhide, Hayaka Masashi, Shiokawa Kazuo

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

Latitudinal variation of stochastic properties of the geomagnetic field Reviewed

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

NONLINEAR PROCESSES IN GEOPHYSICS Vol. 21 ( 2 ) page： 347-356 2014

Ground-Based Observations of Hiss-Like Emissions Changed from Chorus Emissions and Related Pulsating Aurora Reviewed

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

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

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

International Conference on Atmospheric Electricity, ICAE 2014 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Yasuhide, Inoue Takahiro, Hayakawa Masashi, Shiokawa Kazuo

IEEJ Transactions on Power and Energy Vol. 133 ( 12 ) page： 994 - 1000 2013.12

Language：English Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

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 (<i>Qds</i>). 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.

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 Reviewed

Nishioka Michi, Maruyama Takashi, Otsuka Yuichi, Tsugawa Takuya, Ishibashi Hiromitsu, Shiokawa Kazuo, Ishii Mamoru

Antarctic record Vol. 57 ( 3 ) page： 357 - 368 2013.11

Language：English Publishing type：Research paper (scientific journal) Publisher：National Institute of Polar Research

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 Reviewed

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

GEOPHYSICAL RESEARCH LETTERS Vol. 40 ( 22 ) page： 5983 - 5987 2013.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

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 degrees N, 143.8 degrees E), Shigaraki (34.9 degrees N, 136.1 degrees E), and Sata (31.0 degrees N, 130.7 degrees 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.

DOI： 10.1002/2013GL058087

Web of Science

Scopus

Comparison of meridional thermospheric winds observed by ionosondes and Fabry-Perot interferometers Reviewed Open Access

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

Antarctic Record Vol. 57 ( 3 ) page： 357 - 368 2013.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 103 page： 1 - 2 2013.10

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

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

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 103 page： 184-194 2013.9

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

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

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 98 page： 105-112 2013.6

Planetary wave induced wind and airglow oscillations in the middle latitude MLT region Reviewed

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

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 98 page： 97 - 104 2013.6

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Upper mesosphere airglow emissions and temperature observed at Rikubetsu (43.5 degrees N,143.8 degrees E) and mesospheric winds observed at Wakkanai (45.4 degrees N,141.8 degrees 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 557.7 nm, O-2 and OH(6,2) band emissions and O-2 rotational temperature also showed significant amplitude of oscillation induced by the wave passages. For the 10-day wave, OI557.7 nm showed an amplitude of oscillation equals to or more than 50% of the mean intensity level, O-2 similar to 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. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jastp.2013.03.014

Web of Science

Scopus

Substorm onset and expansion phase intensification precursors seen in polar cap patches and arcs Reviewed

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

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 118 ( 5 ) page： 2034 - 2042 2013.5

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 Vol. 7 ( 1 ) page： 60 - 61 2013.4

Evidence of gravity wave ducting in the mesopause region from airglow network observations Reviewed

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

GEOPHYSICAL RESEARCH LETTERS Vol. 40 ( 3 ) page： 601 - 605 2013.2

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

K. Shiokawa, Y. Miyoshi, P. C. Brandt, D. S. Evans, H. U. Frey, J. Goldstein, K. Yumoto

Journal of Geophysical Research: Space Physics Vol. 118 ( 1 ) page： 256 - 270 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Blackwell Publishing Ltd

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

Web of Science

Scopus

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

S. Lee, K. Shiokawa, J. P. McFadden, K. Seki

Journal of Geophysical Research: Space Physics Vol. 118 ( 1 ) page： 132 - 145 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Blackwell Publishing Ltd

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 (&gt
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

Web of Science

Scopus

GPS observations of medium-scale traveling ionospheric disturbances over Europe Reviewed

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

ANNALES GEOPHYSICAE Vol. 31 ( 2 ) page： 163 - 172 2013

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

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

ANNALES GEOPHYSICAE Vol. 31 ( 9 ) page： 1543 - 1548 2013

Language：English Publishing type：Research paper (scientific journal) Publisher：COPERNICUS GESELLSCHAFT MBH

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.

DOI： 10.5194/angeo-31-1543-2013

Web of Science

Scopus

　 PREV - NEXT 　

<SHIOKAWA, Kazuo>

Papers - SHIOKAWA, Kazuo