Faculty Profiles - OTSUKA, Yuichi

Papers - OTSUKA, Yuichi

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Midnight latitude-altitude distribution of 630 nm airglow in the Asian sector measured with FORMOSAT-2/ISUAL Reviewed

Toru Adachi, Masashi Yamaoka, Mamoru Yamamoto, Yuichi Otsuka, Huixin Liu, Chun-Chieh Hsiao, Alfred B. Chen, Rue-Ron Hsu

Journal of Geophysical Research: Space Physics Vol. 115 ( 9 ) 2010

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

The Imager for Sprites and Upper Atmospheric Lightning (ISUAL) payload on board the FORMOSAT-2 satellite carried out the first limb imaging observation of 630 nm airglow for the purpose of studying physical processes in the F region ionosphere. For a total of 14 nights in 2006-2008, ISUAL scanned the midnight latitude-altitude distribution of 630 nm airglow in the Asian sector. On two nights of relatively active conditions (ΣKp = 26, 30+) we found several bright airglow regions, which were highly variable each night in terms of luminosity and location. In relatively quiet conditions (ΣKp = 4-20) near May/June we found two bright regions which were stably located in the midlatitude region of 40°S-10°S (50°S-20°S magnetic latitude (MLAT)) and in the equatorial region of 0°-10°N (10°S-0° MLAT). On one of the quiet nights, FORMOSAT-3/COSMIC and CHAMP simultaneously measured the plasma density in the same region where ISUAL observed airglow. The plasma density data generally show good agreement, suggesting that plasma enhancements were the primary source of these two bright airglow regions. From detailed comparison with past studies we explain that the airglow in the equatorial region was due to the midnight brightness wave produced in association with the midnight temperature maximum, while that in the midlatitude region was due to the typical plasma distribution usually formed in the midnight sector. The fact that the equatorial airglow was much brighter than the midlatitude airglow and was observed on most nights during the campaign period strongly suggests the importance of further studies on the MTM/MBW phenomenology, which is not well reproduced in the current general circulation model. Copyright 2010 by the American Geophysical Union.

DOI： 10.1029/2009JA015147

Scopus

Lower-thermospheric wind fluctuations measured with an FPI during pulsating aurora at Tromso, Norway Reviewed

S. Oyama, K. Shiokawa, J. Kurihara, T. T. Tsuda, S. Nozawa, Y. Ogawa, Y. Otsuka, B. J. Watkins

ANNALES GEOPHYSICAE Vol. 28 ( 10 ) page： 1847 - 1857 2010

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

Simultaneous observations were conducted with a Fabry-Perot Interferometer (FPI) at a wavelength of 557.7 nm, an all-sky camera at a wavelength of 557.7 nm, and the European Incoherent Scatter (EISCAT) UHF radar during the Dynamics and Energetics of the Lower Thermosphere in Aurora 2 (DELTA-2) campaign in January 2009. This paper concentrated on two events during periods of pulsating aurora. The lower-thermospheric wind velocity measured with the FPI showed obvious fluctuations in both vertical and horizontal components. Of particular interest is that the location of the fluctuations was found in a darker area that appeared within the pulsating aurora. During the same time period, the EISCAT radar observed sporadic enhancements in the F-region backscatter echo power, which suggests the presence of low-energy electron (1 keV or lower) precipitation coinciding with increase in amplitude of the electromagnetic wave (at the order of 10 Hz or higher). While we have not yet identified the dominant mechanism causing the fluctuations in FPI-derived wind velocity during the pulsating aurora, the frictional heating energy dissipated by the electric-field perturbations may be responsible for the increase in ionospheric thermal energy thus modifying the local wind dynamics in the lower thermosphere.

DOI： 10.5194/angeo-28-1847-2010

Web of Science

Reorganization of polar cap patches through shears in the background plasma convection Reviewed

K. Hosokawa, J. P. St-Maurice, G. J. Sofko, K. Shiokawa, Y. Otsuka, T. Ogawa

Journal of Geophysical Research: Space Physics Vol. 115 ( 1 ) 2010

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

On the night of December 20, 2006, 630 nm airglow images obtained by an all-sky camera at Resolute Bay, Canada (74.73°N, 265.07°E
altitude adjusted corrected geomagnetic (AACGM) latitude 82.9°) showed the passage of successive polar cap patches. Shortly after convection came to a temporary halt, one of the patches was reorganized into two substructures in approximately 8 min. The two-dimensional background ionospheric convection pattern measured using the newly deployed PolarDARN radar at Rankin Inlet (62.82°N, 93.11°W
AACGM latitude 72.96°) showed that a velocity shear of approximately 120 m s-1/340 km suddenly appeared in the vicinity of the patch at the time of reorganization. A qualitative analysis of the relationship between the magnitude of the velocity shear and the distance between the divided patches indicates that the shear in the background plasma convection velocity significantly contributed to the reorganization of the patch. This shear structure appeared soon after a southward turning of the interplanetary magnetic field (IMF) and was probably associated with the reconfiguration of the convection pattern from a pre-existing northward-oriented IMF pattern to a southward-oriented one. The present observations indicate that the reconfiguration/deformation of patches because of a shear in the background convection field, especially reorganization of patches into smaller substructures, may play an important role in the rapid structuring of patches. Copyright 2010 by the American Geophysical Union.

DOI： 10.1029/2009JA014599

Scopus

The STEL induction magnetometer network for observation of high-frequency geomagnetic pulsations Reviewed

K. Shiokawa, R. Nomura, K. Sakaguchi, Y. Otsuka, Y. Hamaguchi, M. Satoh, Y. Katoh, Y. Yamamoto, B. M. Shevtsov, S. Smirnov, I. Poddelsky, M. Connors

EARTH PLANETS AND SPACE Vol. 62 ( 6 ) page： 517 - 524 2010

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

The Solar-Terrestrial Environment Laboratory (STEL) induction magnetometer network has been developed to investigate the propagation characteristics of high-frequency geomagnetic pulsations in the Pc1 frequency range (0.2-5 Hz). Five induction magnetometers were installed in the period 2005-2008 at Athabasca in Canada, Magadan and Paratunka in Far East Russia, and Moshiri and Sata in Japan. The sensitivity of these magnetometers is between 0.3 and 13 V/nT at turnover frequencies of 1.7-5.5 Hz. GPS time pulses are used for accurate triggering of the 64-Hz data sampling. We show examples of PiB/Pc1 magnetic pulsations observed at these five stations, as well as the harmonic structure of ionospheric Alfven resonators observed at Moshiri. We found that the Pc1 packets are slightly modulated as they propagate from high to low latitudes in the ionospheric duct. These network observations are expected to contribute to our understanding of Pc1-range magnetic pulsations and their interaction with relativistic electrons by combining the obtained results with future satellite missions that observe radiation belt particles.

DOI： 10.5047/eps.2010.05.003

Web of Science

国際宇宙ステーションJEM曝露部からの超高層大気撮像観測計画ISS-IMAP

齊藤昭則, 阿部琢美, 山崎敦, 鈴木睦, 坂野井健, 藤原均, 吉川一朗, 大塚雄一, 田口真, 山本衛, 中村卓司, 菊池雅行, 江尻省, 河野英昭, 石井守, 久保田実, 星野尾一明, 坂野井和代

第10回宇宙科学シンポジウム講演集 2010

Thermospheric temperature and density variations Reviewed

Hitoshi Fujiwara, Yasunobu Miyoshi, Hidekatsu Jin, Hiroyuki Shinagawa, Yuichi Otsuka, Akinori Saito, Mamoru Ishii

SOLAR AND STELLAR VARIABILITY: IMPACT ON EARTH AND PLANETS ( 264 ) page： 310 - + 2010

Language：English Publishing type：Research paper (international conference proceedings) Publisher：CAMBRIDGE UNIV PRESS

The thermosphere is the transition region from the atmosphere to space. Both the solar ultraviolet radiation and the solar wind energy inputs have caused significant thermospheric variations from past to present. In order to understand thermospheric/ionospheric disturbances in association with changes in solar activity, observational and modelling efforts have been made by many researchers. Recent satellite observations, e.g., the satellite CHAMP, have revealed mass density variations in the upper thermosphere. The thermospheric temperature, wind, and composition variations have been also investigated with general/global circulation models (GCMs) which include forcings due to the solar wind energy inputs and the lower atmospheric effects. In particular, we have developed a GCM which covers all the atmospheric regions, troposphere, stratosphere, mesosphere, and thermosphere, to describe variations of the thermospheric temperature and density caused by both effects from the lower atmosphere and the magnetosphere. GCM simulations represent global and localized temperature and density structures, winch vary from hour to hour, depending on forcings due to the lower atmosphere, solar and geomagnetic activities. This modelling attempt will enable us to describe the thermospheric weather influenced by solar activity in cooperation with ground-based and satellite observations.

DOI： 10.1017/S1743921309992857

Web of Science

Ionospheric and geomagnetic disturbances during the 2005 Sumatran earthquakes Reviewed

Alina Marie Hasbi, Mohammed Awad Momani, Mohd Alauddin Mohd Ali, Norbahiah Misran, Kazuo Shiokawa, Yuichi Otsuka, Kiyohumi Yumoto

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 71 ( 17-18 ) page： 1992 - 2005 2009.12

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

This paper investigates the ionospheric and geomagnetic responses during the 28 March 2005 and 14 May 2005 Sumatran earthquakes using GPS and magnetometer stations located in the near zone of the epicenters. These events occurred during low solar and geomagnetic activity. TEC oscillations with periods of 5-10 min were observed about 10-24 min after the earthquakes and have horizontal propagation velocities of 922-1259 m/s. Ionospheric disturbances were observed at GPS stations located to the northeast of the epicenters, while no significant disturbances were seen relatively east and south of the epicenters. The magnetic field measurements show rapid fluctuations of 4-5 s shortly after the earthquake, followed by a Pc5 pulsation of 4.8 min about 11 min after the event. The correlation between the ionospheric and geomagnetic responses shows a good agreement in the period and time lag of the peak disturbance arrival, i.e. about 11-13 min after the earthquake. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jastp.2009.09.004

Web of Science

On the gravity wave-driven instability of E layer at mid-latitude Reviewed

S. Shalimov, T. Ogawa, Y. Otsuka

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 71 ( 17-18 ) page： 1943 - 1947 2009.12

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

The plasma instability process during internal gravity wave propagation through the ionospheric E region is considered. The growth rate of the instability has been found and it has been shown that it depends on perturbation wavelength, gravity wave parameters and direction of propagation. The conditions for the instability are favorable when the vorticity of the associated neutral motion becomes antiparallel to the geomagnetic field. In the proposed instability mechanism plasma irregularities could seed the large-scale sporadic E layer structuring because they are generated in situ as a part of the same neutral wind structure that serves to initiate the formation of the layer. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jastp.2009.08.004

Web of Science

First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite Reviewed

Smitha V. Thampi, Mamoru Yamamoto, Roland T. Tsunoda, Yuichi Otsuka, Takuya Tsugawa, Jyunpei Uemoto, Mamoru Ishii

GEOPHYSICAL RESEARCH LETTERS Vol. 36 2009.9

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

First observations of large-scale wave structure (LSWS) and the subsequent development of equatorial spread F (ESF), using total electron content (TEC) derived from the ground based reception of beacon signals from the CERTO (Coherent Electromagnetic Radio Tomography) radio beacon on board C/NOFS (Communications/Navigation Outage Forecasting System) satellite, are presented. Selected examples of TEC variations, using measurements made during January 2009 from Bac Lieu, Vietnam (9.2 degrees N, 105.6 degrees E geographic, 1.7 degrees N magnetic dip latitude) are presented to illustrate two key findings: (1) LSWS appears to play a more important role in the development of ESF than the post-sunset rise (PSSR) of the F-layer, and (2) LSWS can appear well before E region sunset. Other findings, that LSWS does not have significant zonal drift in the initial stages of growth, and can have zonal wavelengths of several hundred kilometers, corroborate earlier reports. Citation: Thampi, S. V., M. Yamamoto, R. T. Tsunoda, Y. Otsuka, T. Tsugawa, J. Uemoto, and M. Ishii (2009), First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite, Geophys. Res. Lett., 36, L18111, doi: 10.1029/2009GL039887.

DOI： 10.1029/2009GL039887

Web of Science

Coordinated observations of nighttime medium-scale traveling ionospheric disturbances in 630-nm airglow and HF radar echoes at midlatitudes Reviewed

Suzuki S, Hosokawa K, Otsuka Y, Shiokawa K, Ogawa T, Nishitani N, Shibata T. F, Koustov A. V, Shevtsov B. M

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 114 page： A07312 2009.7

First simultaneous observations of daytime MSTIDs over North America using GPS-TEC and DEMETER satellite data Reviewed

Tatsuo Onishi, Takuya Tsugawa, Yuichi Otsuka, Jean-Jacques Berthelier, Jean-Pierre Lebreton

GEOPHYSICAL RESEARCH LETTERS Vol. 36 2009.6

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

We present simultaneous observations of daytime medium-scale traveling ionospheric disturbances (MSTIDs) over North America, using measurements of the Total Electron Content (TEC) by the US GPS network and ionospheric plasma data from the DEMETER microsatellite. Several events show latitudinal variations of the plasma parameters at satellite altitude corresponding to the MSTID structures revealed on 2D TEC maps. In a case study with a very well defined MSTID, quasi periodic variations of the plasma density and of the ion velocity parallel to the Earth's magnetic field are observed along the satellite orbit that match the signature of the MSTID on the TEC maps. We believe it is the first simultaneous observation of parallel plasma motion in the topside ionosphere and propagating MSTID structures in the F-region. An initial analysis of this event is performed in the light of results from simple model of ionospheric disturbances associated with Atmospheric Gravity Waves (AGWs). Citation: Onishi, T., T. Tsugawa, Y. Otsuka, J.-J. Berthelier, and J.-P. Lebreton (2009), First simultaneous observations of daytime MSTIDs over North America using GPS-TEC and DEMETER satellite data, Geophys. Res. Lett., 36, L11808, doi:10.1029/2009GL038156.

DOI： 10.1029/2009GL038156

Web of Science

Spatial relationship of nighttime medium-scale traveling ionospheric disturbances and F region field-aligned irregularities observed with two spaced all-sky airglow imagers and the middle and upper atmosphere radar Reviewed

Y. Otsuka, K. Shiokawa, T. Ogawa, T. Yokoyama, M. Yamamoto

Journal of Geophysical Research: Space Physics Vol. 114 ( 5 ) 2009.5

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

We report simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) and field-aligned irregularities (FAls) in the F region using two all-sky airglow imagers and the middle and upper atmosphere (MU) radar. MSTIDs propagating southwestward were observed simultaneously in 630-nm airglow images over Sakata (39.0°N, 139.9°E) and Shigaraki (34.90N, 136.1°E), Japan, on the night of 16 June 2004. By using all-sky images over both sites, we estimated the altitude of the airglow layer to be 260 km by the triangulation method. During the MSTID event, FAIs in the F region were observed by making multibeam measurements with the MU radar at Shigaraki. In order to investigate the spatial relationship between the MSTIDs and FAIs, the FAIs were mapped onto the 630-nm airglow layer (altitude, 260 km) along the geomagnetic field lines. We found that FAIs with an intense (weak) signal-to-noise ratio coincided with the airglow depletion (enhancement) caused by the MSTIDs. FAI velocity obtained from a combination of the Doppler velocities on the three radar beams oscillated in the northwest-southeast direction, with an amplitude of approximately 82 m/s. The FAI velocity was northwestward (southeastward) at the airglow depletion (enhancement). The directions of the FAI velocity were consistent with those of the ExB drifts caused by the polarized electric fields associated with the MSTIDs. The northeastward polarized electric field at the airglow depletion region strengthened the background eastward effective electric field and drove the gradient drift instability generating FAIs. This might be the reason why the FAIs preferred to occur at the airglow depletion region. Copyright 2009 by the American Geophysical Union.

DOI： 10.1029/2008JA013902

Scopus

VHF radar observations of nighttime F-region field-aligned irregularities over Kototabang, Indonesia Reviewed

Otsuka, Y., T. Ogawa, and Effendy

Earth Planets Space Vol. 61 page： 431-437 2009.5

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

We report the response of the ionosphere to the large erthquake that occurred in West Sumatra, Indonesia, at 0058 UT on December 26, 2004. We have analyzed Global Positioning System (GPS) data obtained at two sites in Sumatra and at three sites in Thailand to investigate total electron content (TEC) variations. Between 14 and 40 min after the earthquake,
TEC enhancements of 1.6--6.9 TEC units (TECU) were observed
at subionospheric points located 360-2000 km north of the epicenter. From the time delays of the observed TEC enhancements, we find that the TEC enhancements propagated northward from the epicenter. The time delays between the earthquake and rapid increases in TEC, which occurred near the epicenter, are consistent with the idea that acoustic waves generated by the earthquake propagated into the ionosphere at the speed of sound to cause the TEC variations.
A small TEC enhancement of 0.6 TECU was observed south of the epicenter, while no TEC enhancements were seen east of the epicenter. From a model calculation, we find that this directivity of the TEC variations with respect to the azimuth from the epicenter could be caused partially by the directivity in the response of the electron density variation
to the acoustic waves in the neutral atmosphere.

Otsuka, Y., K. Shiokawa, T. Ogawa, T. Yokoyama, and M. Yamamoto

J. Geophys. Res. Vol. 114 page： A05302, doi:10.1029/2008JA013902 2009.5

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

We report simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) and field-aligned irregularities (FAIs) in the F region by using two all-sky airglow imagers and the MU radar. MSTIDs propagating southwestward were observed simultaneously in 630-nm airglow images over Sakata (39.0N, 139.9E) and Shigaraki (34.9N, 136.1E), Japan on the night of June 16, 2004. By using all-sky images over both sites, we estimated the altitude of the airglow layer to be 260 km by the triangulation method.
During the MSTID event, FAIs in the F region were observed
by making multibeam measurements with the MU radar at Shigaraki. In order to investigate the spatial relationship between the MSTIDs and FAIs, the FAIs were mapped onto the 630-nm airglow layer (altitude: 260 km) along the geomagnetic field lines. We found that FAIs with intense (weak) signal-to-noise ratio (SNR) coincided with the airglow depletion (enhancement) caused by the MSTIDs. FAI velocity obtained from a combination of the Doppler velocities on the three radar beams oscillated in the NW-SE direction with an amplitude of approximately 82 m/s. The FAI velocity was northwestward (southeastward) at the airglow depletion (enhancement). The directions of the FAI velocity
were consistent with those of the ExB drifts caused by the polarized electric fields associated with the MSTIDs.
The northeastward polarized electric field at the airglow depletion region strengthened the background eastward
effective electric field, and drove the gradient drift instability generating FAIs. This might be the reason why the FAIs preferred to occur at the airglow depletion region.

Y. Otsuka, K. Shiokawa, T. Ogawa, T. Yokoyama, M. Yamamoto

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 114 2009.5

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

We report simultaneous observations of medium-scale traveling ionospheric disturbances (MSTIDs) and field-aligned irregularities (FAIs) in the F region using two all-sky airglow imagers and the middle and upper atmosphere (MU) radar. MSTIDs propagating southwestward were observed simultaneously in 630-nm airglow images over Sakata (39.0 degrees N, 139.9 degrees E) and Shigaraki (34.9 degrees N, 136.1 degrees E), Japan, on the night of 16 June 2004. By using all-sky images over both sites, we estimated the altitude of the airglow layer to be 260 km by the triangulation method. During the MSTID event, FAIs in the F region were observed by making multibeam measurements with the MU radar at Shigaraki. In order to investigate the spatial relationship between the MSTIDs and FAIs, the FAIs were mapped onto the 630-nm airglow layer (altitude, 260 km) along the geomagnetic field lines. We found that FAIs with an intense (weak) signal-to-noise ratio coincided with the airglow depletion (enhancement) caused by the MSTIDs. FAI velocity obtained from a combination of the Doppler velocities on the three radar beams oscillated in the northwest-southeast direction, with an amplitude of approximately 82 m/s. The FAI velocity was northwestward (southeastward) at the airglow depletion (enhancement). The directions of the FAI velocity were consistent with those of the E x B drifts caused by the polarized electric fields associated with the MSTIDs. The northeastward polarized electric field at the airglow depletion region strengthened the background eastward effective electric field and drove the gradient drift instability generating FAIs. This might be the reason why the FAIs preferred to occur at the airglow depletion region.

DOI： 10.1029/2008JA013902

Web of Science

Motion of polar cap patches: A statistical study with all-sky airglow imager at Resolute Bay, Canada Reviewed

Hosokawa, K, Kashimoto, T, Suzuki, S, Shiokawa, K, Otsuka, Y, Ogawa, T

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 114 2009.4

Motion of polar cap patches: A statistical study with all-sky airglow imager at Resolute Bay, Canada Reviewed

Hosokawa K, Kashimoto T, Suzuki S, Shiokawa K, Otsuka Y, Ogawa T

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 114 2009.4

Unusually elongated, bright airglow plume in the polar cap F region: Is it a tongue of ionization? Reviewed

K. Hosokawa, T. Tsugawa, K. Shiokawa, Y. Otsuka, T. Ogawa, M. R. Hairston

GEOPHYSICAL RESEARCH LETTERS Vol. 36 2009.4

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

We report an event of unusually elongated, bright airglow plume, which is considered as an optical manifestation of tongue of ionization (TOI) in the central polar cap. This optical structure was detected with an all-sky airglow imager at Resolute Bay (74.73 degrees N, 265.07 degrees E) during a large magnetic storm on December 15, 2006. The absolute optical intensity of the plume was approximate to 1 kR, which is much brighter than that of non-stormtime polar cap patches. Two-dimensional imaging capability of the all-sky imager demonstrates that some meso-scale structures (approximate to 250-600 km) were embedded within the plume. Simultaneous ion density and drift measurements with the DMSP spacecraft strongly suggest that the plume was extending from the dayside as a narrow stream of dense plasma and thus is an optical manifestation of polar cap TOI. The DMSP data also implies that the possible source of the plume is a narrow stream of storm enhanced density (SED) transported from lower latitudes. The DMSP auroral particle observation demonstrates that the polar cap extremely expanded equatorward during this interval. This extreme expansion allowed the anti-sunward convection to capture plasmas within the SED and deliver them deep into the polar cap as a luminous airglow plume. This observation claims that the plasma transport from the dayside lower latitudes plays an important role in controlling the plasma environment in the polar cap ionosphere during magnetic storms. Citation: Hosokawa, K., T. Tsugawa, K. Shiokawa, Y. Otsuka, T. Ogawa, and M. R. Hairston (2009), Unusually elongated, bright airglow plume in the polar cap F region: Is it a tongue of ionization?, Geophys. Res. Lett., 36, L07103, doi:10.1029/2009GL037512.

DOI： 10.1029/2009GL037512

Web of Science

Medium-scale traveling ionospheric disturbances observed with the SuperDARN Hokkaido radar, all-sky imager, and GPS network and their relation to concurrent sporadic E irregularities Reviewed

Ogawa T, Nishitani N, Otsuka Y, Shiokawa K, Tsugawa T, Hosokawa K

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 114 2009.3

Medium-scale traveling ionospheric disturbances observed with the SuperDARN Hokkaido radar, all-sky imager, and GPS network and their relation to concurrent sporadic E irregularities Reviewed

T. Ogawa, N. Nishitani, Y. Otsuka, K. Shiokawa, T. Tsugawa, K. Hosokawa

Journal of Geophysical Research: Space Physics Vol. 114 ( 3 ) 2009.3

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

We present midlatitude medium-scale traveling ionospheric disturbances (MSTIDs) observed with a Super Dual Auroral Radar Network (SuperDARN) HF radar at around 10 MHz in Hokkaido, Japan, in combination with a 630-nm all-sky imager and a GPS network (GEONET) that provides total electron content (TEC) data. MSTIDs propagating southward from high latitudes are detected at first with the HF radar and then with the imager and GEONET. We analyze two MSTID events, one in winter (event 1) and the other in summer (event 2), to find that MSTIDs appear simultaneously, at least, at 55°-25°N. It is shown that nighttime MSTIDs propagate toward the southwest over a horizontal distance of about 4000 km, and daytime MSTIDs do so toward the southeast. Daytime radar echoes are due to ground/sea surface (GS) scatter, while nighttime echoes in event 1 return from 15-m-scale F region field-aligned irregularities (FAIs) and those in event 2 are due to GS scatter. Doppler velocities of the nighttime F region FAI echoes in event 1 are negative (motion away from the radar) within strong echo regions and are positive (motion toward the radar) within weak echo regions. This fact suggests that the strong (weak) echoes return from suppressed (enhanced) airglow/TEC areas, in line with previous observations over central Japan. The nighttime MSTIDs in events 1 and 2 are often accompanied by concurrent coherent echoes from FAIs in sporadic E (Es) layers. The Es echo areas in event 2 rather coincide with suppressed airglow/TEC areas in the F region that are connected with the echo areas along the geomagnetic field, indicating the existence of E and F region coupling at night. Copyright 2009 by the American Geophysical Union.

DOI： 10.1029/2008JA013893

Scopus

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Papers - OTSUKA, Yuichi