研究者詳細 - 塩川　和夫

論文 - 塩川　和夫

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Decrease in Bz prior to the dipolarization in the near-Earth plasma sheet -: art. no. A09219 査読有り Open Access

Shiokawa, K; Miyashita, Y; Shinohara, I; Matsuoka, A

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 110 巻 ( A9 ) 2005年9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

[1] We examine in detail the rapid decrease in Bz just before dipolarizations observed by the Geotail satellite in the near-Earth plasma sheet at (XGSM, YGSM) = (-8.3 RE, -5.1 R E). The observations were made using high-time-resolution data from a fluxgate magnetometer (16-Hz sample), a search-coil magnetometer (128 Hz), and an electric field antenna (64 Hz). Two dipolarizations were observed during a short time interval of 2 min. The magnetic Bz component suddenly decreased 2-4 s prior to the dipolarization. Characteristic waves with frequencies of 5-20 Hz and amplitudes of 1-3 mV m-1 and 5-15 nT s-1 were observed in the electric and magnetic field data at the time of the sudden decreases in Bz. We discuss two possible causes of the sudden decreases in Bz prior to the dipolarizations: (1) passage of a field-aligned line current associated with the substorm current wedge and (2) explosive growth phase and subsequent disruption of the tail current caused by the observed characteristic field oscillations. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2005JA011144

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Observations of equatorial plasma bubbles using broadcast VHF radio waves 査読有り

Nakata H, Nagashima I, Sakata K, Otsuka Y, Akaike Y, Takano T, Shimakura S, Shiokawa K, Ogawa T

GEOPHYSICAL RESEARCH LETTERS 32 巻 ( 17 ) 頁： 1 - 4 2005年9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

The propagation of VHF radio waves affected by field-aligned irregularities within equatorial plasma bubbles is examined. Continuous observation of VHF radio waves at Tateyama, Japan, shows that broadcast radio waves transmitted from Southeast Asia propagate to Japan. Using a ray-tracing calculation combined with a model of scattering by field-aligned irregularities, we determined scatter points suitable for the reception of these radio waves. The results of the calculation show that radio waves transmitted from the Philippines can propagate to Japan owing to field-aligned irregularities within equatorial plasma bubbles located west of Japan. Comparing with all-sky imager data observed at Sata, Japan, we found that the radio waves are received at Tateyama when the plasma bubbles are observed at Sala. The results of this study show that the reception of these radio waves is closely correlated with the equatorial plasma bubbles. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2005GL023243

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Development of the Virtual Earth's Magnetosphere System (VEMS) 査読有り

Murata Ken T., Yamamoto Kazunori, Matsuoka Daisuke, Kimura Eizen, Matsumoto Hiroshi, Okada Masaki, Mukai Toshifumi, Sigwarth John B., Fujita Shigeru, Tanaka Takashi, Yumoto Kiyohumi, Ogino Tatsuki, Shiokawa Kazuo, Tsyganenko Nikolai A., Green James L., Nagai Tsugunobu

Advances in polar upper atmosphere research 19 巻頁： 135 - 151 2005年8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：National Institute of Polar Research

We have constructed a new research environment for geo-space science based on 3-D visualization tool and network database; Virtual Earth's Magnetosphere System (VEMS). With an interactive research environment researchers can visually understand structures of the Earth's magnetosphere using VEMS. On the VEMS, computer simulation results and observation data are simultaneously visualized, having a potential to data assimilation for geo-space studies in the future. Since the VEMS deals with time-dependent data, it also helps researchers to study dynamics of the Earth's magnetosphere. We found that immersive data analyses are possible using the VEMS on a virtual reality system.

CiNii Research

Magnetic field fluctuations during substorm-associated dipolarizations in the nightside plasma sheet around X=-10 RE -: art. no. A05212 査読有り

Shiokawa, K; Shinohara, I; Mukai, T; Hayakawa, H; Cheng, CZ

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 110 巻 ( A5 ) 2005年5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

[1] Using high-time-resolution data for the magnetic field (1/16 s), plasma moment (12 s), and electric field (3 s) obtained by Geotail, we have investigated various characteristics of magnetic field fluctuations for 21 events of substorm-associated near-Earth dipolarization at XGSM= -8 - -11 RE and |YGSM| < 5 RE. The dipolarizations were always accompanied by fluctuations of the magnetic field. The amplitude of the fluctuations tends to be larger for smaller ambient magnetic field. For several events we found that magnetic field elevation angles show rapid decrease prior to the rapid increase (features like explosive growth phase). Compressional fluctuations of magnetic field intensity B show characteristic spikes of a sudden decrease and increase with a timescale of seconds. For quite a few cases the fluctuations are accompanied by enhancements of earthward plasma velocity. The spectral shape of the B fluctuations had a steeper slope (f-2.7) at higher frequency range at 1.0-0.2 Hz than at 0.01-0.2 Hz (f-2.0) for the events closer to the cross-tail current sheet (smaller ambient-B region). We found that the steeper slope extends to lower frequency range below 0.2 Hz for the events away from the current sheet (larger ambient-B region). This fact may suggest transition from three-dimensional to two-dimensional turbulence from smaller B to larger B region. We also investigated correlation of fluctuations in plasma velocity and magnetic field for waves with periods around 60 s. The correlations were rather weak, suggesting that non-MHD plasma processes are going on. For these waves, the magnetic and plasma pressure variations were clearly antiphase. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2004JA010378

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Geomagnetic conjugate observation of nighttime medium-scale and large-scale traveling ionospheric disturbances: FRONT3 campaign 査読有り

Shiokawa K, Otsuka Y, Tsugawa T, Ogawa T, Saito A, Ohshima K, Kubota M, Maruyama T, Nakamura T, Yamamoto M, Wilkinson P

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 110 巻 ( A5 ) 2005年5月

担当区分：筆頭著者記述言語：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

The third FRONT (F-region Radio and Optical measurement of Nighttime TID) campaign was carried out during the new-moon period of May-June 2003, in order to investigate the geomagnetic conjugacy of medium-scale and large-scale traveling ionospheric disturbances (MSTIDs/LSTIDs) at midlatitudes. Seven all-sky airglow imagers were operated in Japan and Australia. For almost all clear-sky nights, we observed MSTIDs in the 630-nm airglow images with horizontal wavelengths of 100-400 km propagating southwestward in Japan and northwestward in Australia. All of them show a one-to-one correspondence of wave structures between the Northern and Southern Hemispheres, indicating strong electrodynamic coupling between the two hemispheres through the geomagnetic field line. We also found that airglow intensity variations with a timescale longer than that of MSTIDs often show a good correlation between the two hemispheres. On 28 May, we succeeded in detecting an equatorward propagating LSTID (spatial scale ∼1000 km) as airglow enhancements at the conjugate stations. The airglow peak of the LSTID in the Northern Hemisphere was ∼20 min earlier than that in the Southern Hemisphere, indicating that the observed LSTID is caused by a wave in the neutral atmosphere rather than by an electric field structure. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2004JA010845

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Low-latitude auroras observed in Japan: 1999-2004 査読有り

Shiokawa, K; Ogawa, T; Kamide, Y

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 110 巻 ( A5 ) 2005年5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

[1] From routine observations by means of highly sensitive all-sky cameras and tilting-filter photometers, a total of 20 low-latitude aurora events in Japan were identified during the high solar activity period of 1999-2004. This indicates that the invisible-level auroras appear rather frequently in the northern sky of Japan during magnetic storms. These auroras are characterized by an enhancement in red (630.0 nm) emissions in the northern sky during magnetic storms, probably at geomagnetic latitudes higher than ∼40-50°. We show examples of stable auroral red (SAR) arcs, which are typically observed during the recovery phase of storms. We also found several red aurora events that occurred at the initial phase of magnetic storms. Intensifications as well as equatorward motion of the auroras were observed in association with storm time substorms. Green line emissions (557.7 nm) were often enhanced (∼1 kR) not only in the northern sky but also in the whole sky. Some auroras show weak enhancements (∼10 R) of N2+1N (427.8 nm) in the northern sky in the morning hours. We discuss possible causes of these emissions in light of magnetospheric disturbances and thermospheric dynamics. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2004JA010706

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P253 中間圏の大気光画像中に現れた湾曲波面を持つ大気重力波の構造査読有り

鈴木臣, 塩川和夫, 中村健治, 大塚雄一, 小川忠彦, 中村卓司

大会講演予講集 87 巻頁： 374 2005年4月

館山におけるVHF帯電波受信のプラズマバブル緯度依存性について査読有り

坂田健一郎, 中田裕之, 鷹野敏明, 島倉信, 大塚雄一, 塩川和夫, 小川忠彦

大気電気研究 66 巻頁： 63 - 64 2005年3月

Auroral particles associated with a substorm brightening arc 査読有り

Yago K, Shiokawa K, Hayashi K, Yumoto K

GEOPHYSICAL RESEARCH LETTERS 32 巻 ( 6 ) 頁： 1 - 4 2005年3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 investigated the characteristics of auroral precipitating particles associated with a brightened arc at a pseudo-substorm, using auroral images of a high-time resolution (0.25 s) all-sky TV camera, particle data from the DMSP F10 spacecraft, and high-latitude magnetograms. The arc brightening occurred at 0407 UT (∼20 MLT) on December 30, 1994, at Fort Smith (67 MLAT), Canada, coincident with high-latitude Pi 2 magnetic pulsations. The brightening appeared without expansion (pseudo-breakup), and Fort Smith was located duskside of the main onset region. From the simultaneous DMSP particle data, the brightened arc is found to correspond to an electron inverted-V structure near the equatorward edge of the electron precipitation region, suggesting the pseudo-breakup of the auroral substorm occurred in the inner part of the plasma sheet. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2004GL021894

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Relationship between propagation direction of gravity waves in OH and OI airglow images and VHF radar echo occurrence during the SEEK-2 campaign 査読有り

Onoma F, Otsuka Y, Shiokawa K, Ogawa T, Yamamoto M, Fukao S, Saito S

ANNALES GEOPHYSICAE 23 巻 ( 7 ) 頁： 2385 - 2390 2005年

Geoeffectiveness of shocks in populating the radiation belts 査読有り

Blake J., Slocum P., Mazur J., Looper M., Selesnick R., Shiokawa K.

Multiscale Coupling of Sun-Earth Processes 頁： 125 - 133 2005年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Multiscale Coupling of Sun-Earth Processes

This chapter describes some representative shock-induced injections of the last 13 years and the correlation of the injection events with ground-based magnetograms from the 210 Magnetic Meridian Chain. Several shock-associated injection events have been observed during the last solar cycle that exhibited a variety of differing features, including promptness of the injection relative to the arrival of the shock at the Earth, location of the new belt in the magnetosphere (L value), particle species injected, and the relationship to "normal" relativistic electron injections. Two things have become apparent: long-lived belts require injection into L ∼ 2.5, deep injections are associated with fast risetimes in the ground-based magnetometer observations of the Storm Sudden Commencement (SSC). The need for an injection deep into the magnetosphere is straightforward to understand. Magnetospheric loss processes do not depend upon the injection process. So, in order for an injection to be long-lived, it must be into a region where loss processes usually are weak, thus, deeply into the magnetosphere. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/B978-044451881-1/50010-1

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The first coordinated observations of mid-latitude E-region quasi-periodic radar echoes and lower thermospheric 557.7-nm airglow 査読有り

Ogawa, T; Otsuka, Y; Onoma, F; Shiokawa, K; Yamamoto, M

ANNALES GEOPHYSICAE 23 巻 ( 7 ) 頁： 2391 - 2399 2005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

We present the first coordinated observations of quasi-periodic (QP) radar echoes from sporadic-E (ES,) field-aligned irregularities (FAIs), OI 557.7-nm airglow, and neutral winds in a common volume over Shigaraki, Japan (34.9° N, 136.1° E) on the night of 5 August 2002 during the SEEK-2 campaign. QP echo altitudes of 90-110 km were lower than usual by 10 km, enabling us to make a detailed comparison among QP echoes, airglow intensity, and neutral wind at around 96 km altitude. Eastward movement of the QP echo regions is consistent with the motions of neutral winds, airglow structures, and FAIs, suggesting that the electrodynamics of ES-layers is fundamentally controlled by the neutral atmospheric dynamics. During the QP echo event, the echo altitudes clearly went up (down) in harmony with an airglow enhancement (subsidence) that also moved to the east. This fact suggests that the eastward-moving enhanced airglow region included an upward (downward) component of neutral winds to raise (lower) the altitude of the windshear node responsible for the ES formation. The airglow intensity, echo intensity, and Doppler velocity of FAIs at around 96 km altitude fluctuated with periods from 10 min to 1 h, indicating that these parameters were modulated with short-period atmospheric disturbances. Some QP echo regions below 100 km altitude contained small-scale QP structures in which very strong neutral winds exceeding 100 m/s existed. The results are compared with recent observations, theories, and simulations of QP echoes. © European Geosciences Union 2005.

DOI： 10.5194/angeo-23-2391-2005

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Simultaneous ground- and satellite-based airglow observations of geomagnetic conjugate plasma bubbles in the equatorial anomaly 査読有り

Ogawa T, Sagawa E, Otsuka Y, Shiokawa K, Immel TI, Mende SB, Wilkinson P

EARTH PLANETS AND SPACE 57 巻 ( 5 ) 頁： 385 - 392 2005年

Spatial relationship of equatorial plasma bubbles and field-aligned irregularities observed with an all-sky airglow imager and the Equatorial Atmosphere Radar 査読有り

Otsuka Y, Shiokawa K, Ogawa T, Yokoyama T, Yamamoto M, Fukao S

GEOPHYSICAL RESEARCH LETTERS 31 巻 ( 20 ) 頁： L20802 2004年10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 report, for the first time, simultaneous two-dimensional observations of 630-nm airglow depletions and radar backscatter from field-aligned irregularities (FAI) associated with equatorial plasma bubbles. Spatial distributions of backscatter were obtained by performing east-west scans with the 47-MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia. A 630-nm airglow depletion, caused by a plasma bubble, was simultaneously observed with an all-sky airglow imager. Both the airglow depletion and backscatter region appeared as band-like structure elongated in the meridional direction with a zonal width of about 100 km. To compare the spatial structures of backscatter with that of airglow depletion, the backscatter was projected onto a horizontal plane at 250-km altitude. Backscatter was found to occur within the entire airglow-depleted region. Copyright 2004 by the American Geophysical Union.

DOI： 10.1029/2004GL020869

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その他リンク： http://orcid.org/0000-0001-8392-6455

中間圏の大気光画像中に現れた湾曲波面を持つ大気重力波の構造査読有り

鈴木臣, 塩川和夫, 中村健治, 大塚雄一, 小川忠彦, 中村卓司

大会講演予講集 86 巻頁： . 2004年10月

ブラジル磁気異常帯における雷雲電場に伴う宇宙線・リオメータ強度変動査読有り

巻田和男, 鳥居建男, 星野光男, 西野正徳, 塩川和夫, SCHUCH Nelson Jorge

拓殖大学理工学研究報告 9 巻 ( 2 ) 頁： 37 - 42 2004年10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：拓殖大学

A field mill and a cosmic-ray detector have been newly installed at Brazilian geomagnetic anomaly region. We have compared 38.2 MHz riometer with these data during strong thunderstorm period. Although no clear relationship have been recognized yet between electric field and the fluctuation of cosmic-ray intensity, however a good relationship was found between electric field and 38.2 MHz intensity. This result may suggest that 38.2 MHz radio wave was excited by acceleration of particles under the thunderstorm electric field.

Statistical characteristics of gravity waves observed by an all-sky imager at Darwin, Australia 査読有り Open Access

Suzuki, S; Shiokawa, K; Otsuka, Y; Ogawa, T; Wilkinson, P

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 109 巻 ( D20 ) 頁： D20 - S07 2004年8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: Atmospheres

An all-sky airglow imager with a cooled charge-coupled device camera in place at Darwin (12.4°S, 131.0°E), Australia, since October 2001 has been used to obtain two-dimensional gravity wave images in the mesopause region. Using airglow images of the OI (557.7 nm, emission altitude ∼96 km) and OH band (720-910 nm, ∼86 km) emissions obtained for October 2001 to August 2002, we investigated the wavelengths, phase velocities, and propagation directions of gravity waves. Wave occurrence in OH images (60-90%) is higher than in OI images (30-70%) for all seasons. The waves have wavelengths of less than 90 km (peak: 30-50 km) and phase velocities ofless than 90 m/s (peak: 30-60 m /s). Most of the waves propagate in the meridional direction, and the directionality strongly depends on the season. In winter, waves propagate both poleward and equatorward, while in summer almost all waves propagate poleward. An examination of airglow-imaging statistics at Adelaide (35°S, 138°E), Australia, obtained by Walterscheid et al. [1999], leads us to conclude that this clear directionality is caused by the location of the wave sources and by the wave ducting processes; that is, poleward waves in summer come from an equatorial convective source through a thermal duct structure. The effect of wind filtering on the waves is also discussed for zonal wave propagation. Copyright 2004 by the American Geophysical Union.

DOI： 10.1029/2003JD004336

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Geomagnetic conjugate observations of medium-scale traveling ionospheric disturbances at midlatitude using all-sky airglow imagers 査読有り

Otsuka Y, Shiokawa K, Ogawa T, Wilkinson P

GEOPHYSICAL RESEARCH LETTERS 31 巻 ( 15 ) 2004年8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 report for the first time simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) at geomagnetic conjugate points in both hemispheres, using two all-sky airglow imagers at midlatitudes. A 630-nm all-sky CCD imager at Sata, Japan, detected MSTIDs with a wavefront elongated from NW to SE on the night of August 9, 2002. During this event, MSTIDs with a wavefront elongated from SW to NE were observed at the geomagnetic conjugate point, Darwin, Australia. To investigate geomagnetic conjugacy of the MSTID structures, the Darwin images were mapped The MSTID structures mapped from Darwin to its magnetic conjugate points along the geomagnetic field lines (B) coincide closely with those in the Sata images. This result suggests that polarization electric field (Ep) plays an important role in the generation of MSTIDs. Ep maps along B and moves the F region plasma upward or downward by E × B drifts, causing plasma density perturbations with structures mirrored in the northern and southern hemispheres. Copyright 2004 by the American Geophysical Union.

DOI： 10.1029/2004GL020262

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内部磁気圏ミッションの提案

塩川和夫, 関加奈子, 三好由純, 小原隆博, 小野高幸

第4回宇宙科学シンポジウム proceeding 頁： 349 - 352 2004年8月

Comparison of OH rotational temperatures measured by the spectral airglow temperature imager (SATI) and by a tilting-filter photometer 査読有り

Shiokawa K, Otsuka Y, Ogawa T, Takahashi H, Nakamura T, Shimomai T

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS 66 巻 ( 11 ) 頁： 891 - 897 2004年7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

Measurements of OH rotational temperatures have been carried out at Shigaraki, Japan (34.8°N, 136.1°E), for 8 nights in September-December 2000, using the Spectral Airglow Temperature Imager (SATI) and a tilting-filter zenith photometer (MC4), simultaneously. Clear positive correlation was obtained between the two temperatures. However, the absolute temperatures obtained by SATI were unusually low (∼130-180 K) with differences of ∼60 K from the MC4 temperatures. We discuss possible causes of the temperature differences, particularly for SATI, which newly uses OH(6-2) Q-branch lines (MC4 uses OH(6-2) P-branch lines) and imaging optics for the temperature measurement. © 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jastp.2004.03.003

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