Faculty Profiles - SHIOKAWA, Kazuo

Papers - SHIOKAWA, Kazuo

Division display 361 - 380 of about 483 ／ All the affair displays >>

Decrease in B-z prior to the dipolarization in the near-Earth plasma sheet Reviewed Open Access

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

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 110 ( A9 ) 2005.9

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

[1] We examine in detail the rapid decrease in B-z just before dipolarizations observed by the Geotail satellite in the near-Earth plasma sheet at (X-GSM, Y-GSM) = (-8.3 R-E, - 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 B-z. We discuss two possible causes of the sudden decreases in B-z 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.

DOI： 10.1029/2005JA011144

Web of Science

Scopus

Observations of equatorial plasma bubbles using broadcast VHF radio waves Reviewed

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

GEOPHYSICAL RESEARCH LETTERS Vol. 32 ( 17 ) page： 1 - 4 2005.9

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

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

Web of Science

Scopus

Development of the Virtual Earth's Magnetosphere System (VEMS) Reviewed

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 Vol. 19 page： 135 - 151 2005.8

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

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

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 110 ( A5 ) 2005.5

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

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 X-GSM = -8 similar to -11 R-E and vertical bar Y(GSM)vertical bar < 5 R-E. 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.

DOI： 10.1029/2004JA010378

Web of Science

Scopus

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

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 Vol. 110 ( A5 ) 2005.5

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：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

Web of Science

Scopus

Low-latitude auroras observed in Japan: 1999-2004 Reviewed

Shiokawa K, Ogawa T, Kamide Y

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 110 ( A5 ) 2005.5

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

[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 &SIM; 40 - 50&DEG;. 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 (&SIM; 1 kR) not only in the northern sky but also in the whole sky. Some auroras show weak enhancements (&SIM; 10 R) of N-2(+) 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.

DOI： 10.1029/2004JA010706

Web of Science

Scopus

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 Reviewed

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 Vol. 87 page： 374 2005.4

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 Reviewed

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 Vol. 66 page： 63 - 64 2005.3

Auroral particles associated with a substorm brightening arc Reviewed

K Yago, K Shiokawa, K Hayashi, K Yumoto

GEOPHYSICAL RESEARCH LETTERS Vol. 32 ( 6 ) page： 1 - 4 2005.3

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

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 ( similar to 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.

DOI： 10.1029/2004GL021894

Web of Science

Scopus

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

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

ANNALES GEOPHYSICAE Vol. 23 ( 7 ) page： 2385 - 2390 2005

Geoeffectiveness of shocks in populating the radiation belts Reviewed

JB Blake, PL Slocum, JE Mazur, MD Looper, RS Selesnick, K Shiokawa

Multiscale Coupling of Sun-Earth Processes page： 125 - 133 2005

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ELSEVIER SCIENCE BV

On 24 March 1991, ions and electrons with energies of 10s of MeV were observed by CRRES to be injected into the Earth's magnetosphere. The injection created a stable new radiation belt that persisted for years. Later in the decade, several geomagnetic storms and associated energetic solar particle events led to new radiation belts, but none with comparable stability until two injections occurred in November 2001 that lasted for two years. Using data from SAMPEX, Polar, 1997-068, and the 210 Magnetic Meridian Chain, we examine observations of storms that lead to new long-lasting belts. We find that stable belts arise after a deep injection into the slot region (L similar to 2.5). Associated with these injections is an unusually rapid rise in the magnetic field impulse as seen by ground-based magnetometers.

DOI： 10.1016/B978-044451881-1/50010-1

Web of Science

Scopus

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

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

EARTH PLANETS AND SPACE Vol. 57 ( 5 ) page： 385 - 392 2005

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

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

ANNALES GEOPHYSICAE Vol. 23 ( 7 ) page： 2391 - 2399 2005

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

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

GEOPHYSICAL RESEARCH LETTERS Vol. 31 ( 20 ) page： L20802 2004.10

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 Reviewed

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 Vol. 86 page： . 2004.10

Cosmic Ray and Riometer Observations in Associated with Thunderstorm at Brazilian Geomagnetic Anomaly Region Reviewed

MAKITA Kazuo, TORII Tatuo, HOSHINO Mituo, NISHINO Masonori, SHIOKAWA Kazuo, SCHUCH Nelson Jorge

Bulletin of science and engineering, Takushoku University Vol. 9 ( 2 ) page： 37 - 42 2004.10

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

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 Reviewed Open Access

Shin Suzuki, K. Shiokawa, Y. Otsuka, T. Ogawa, P. Wilkinson

Journal of Geophysical Research D: Atmospheres Vol. 109 ( D20 ) page： D20 - S07 2004.8

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

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

Web of Science

Scopus

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

Y Otsuka, K Shiokawa, T Ogawa, P Wilkinson

GEOPHYSICAL RESEARCH LETTERS Vol. 31 ( 15 ) 2004.8

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

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 (E-p) plays an important role in the generation of MSTIDs. E-p maps along B and moves the F region plasma upward or downward by E x B drifts, causing plasma density perturbations with structures mirrored in the northern and southern hemispheres.

DOI： 10.1029/2004GL020262

Web of Science

Scopus

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 page： 349 - 352 2004.8

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

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

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 66 ( 11 ) page： 891 - 897 2004.7

　 PREV - NEXT 　

<SHIOKAWA, Kazuo>

Papers - SHIOKAWA, Kazuo