A5103187650- Ionosphere and magnetosphere dynamics
- Earthquake Detection and Analysis
- Solar and Space Plasma Dynamics
- GNSS positioning and interference
- Geomagnetism and Paleomagnetism Studies
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- earthquake and tectonic studies
- Meteorological Phenomena and Simulations
- Seismic Waves and Analysis
- Tropical and Extratropical Cyclones Research
- Planetary Science and Exploration
- Astro and Planetary Science
- Ocean Waves and Remote Sensing
- Atmospheric aerosols and clouds
- Geological and Geophysical Studies
- Oceanographic and Atmospheric Processes
- Methane Hydrates and Related Phenomena
- Space Satellite Systems and Control
- Space exploration and regulation
- Atmospheric and Environmental Gas Dynamics
- Hormonal Regulation and Hypertension
- Inertial Sensor and Navigation
- Cardiovascular and Diving-Related Complications
- Eicosanoids and Hypertension Pharmacology
Nagoya University
2016-2025
Earth and Space Research
2016-2024
National Institute for Space Research
2023
The University of Tokyo
2022
National Institute of Science Communication and Information Resources
2022
National Institute for Fusion Science
2022
National Defense Academy of Japan
2022
Koneru Lakshmaiah Education Foundation
2018
Charles River Laboratories (Netherlands)
2018
John Wiley & Sons (United States)
2014-2018
The dual frequency radio signals of the Global Positioning System (GPS) allow measurements total number electrons, called electron content (TEC), along a ray path from GPS satellite to receiver. We have developed new technique construct two-dimensional maps absolute TEC over Japan by using data more than 1000 receivers. A least squares fitting procedure is used remove instrumental biases inherent in and Two-dimensional vertical are derived with time resolution 30 seconds spatial 0.15° ×...
All the details of ionospheric disturbances following 2011 Tohoku Earthquake were first revealed by high-resolution GPS total electron content observation in Japan. The initial disturbance appeared as sudden depletions small impulsive TEC enhancements ~7 minutes after earthquake onset, near epicenter. Then, concentric waves to propagate radial direction with a velocity 138–3,457 m/s. Zonally-extended also west In vicinity epicenter, short-period oscillations period ~4 observed. This paper...
We have investigated statistical characteristics of the nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) observed in 630‐nm airglow images at two stations, Rikubetsu (43.5°N, 34.8°MLAT) and Shigaraki (34.9°N, 25.4°MLAT), Japan for 1998–2000 near solar maximum period. Most MSTIDs propagate southwestward images. The typical wavelength, velocity, period, amplitude are 100–300 km, 50–100 m/s, 0.5–1.5 h, 5–15%, respectively. Seasonal variations these parameters not clear....
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 midlatitudes. A 630‐nm CCD imager Sata, Japan, detected MSTIDs with a wavefront elongated from NW to SE on night August 9, 2002. During this event, SW NE were observed point, Darwin, Australia. To investigate conjugacy MSTID structures, Darwin images mapped The structures its magnetic along...
Nighttime and daytime medium‐scale traveling ionospheric disturbances (MSTIDs) are detected with dense wide detrended total electron content (TEC) maps over North America using multiple GPS receiver networks. The TEC cover a region of 60–130°W 24–54°N (30–65°N in geomagnetic latitude), have spatial resolution 1.05° × latitude longitude (0.15° 0.15° 7 pixel smoothing) temporal 30 seconds. reveal, for the first time, that nighttime MSTIDs propagate southwestward 200–500 km wavelengths...
A physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi‐instrument observations, theoretical modeling, basic principles. According to mechanism, an equatorward neutral wind required produce storms. The mechanical effects (1) reduce (or stop) downward diffusion plasma along geomagnetic field lines, (2) raise ionosphere high altitudes reduced chemical loss, hence (3) accumulate near above peak centered around ±30° magnetic latitudes....
Abstract. Two-dimensional structures of medium-scale traveling ionospheric disturbances (MSTIDs) over Europe have been revealed, for the first time, by using maps total electron content (TEC) obtained from more than 800 GPS receivers European receiver networks. From statistical analysis TEC 2008, we found that observed MSTIDs can be categorized into two groups: daytime MSTID and nighttime MSTID. The frequently occurs in winter. Its maximum occurrence rate monthly hourly bin exceeds 70% at...
Large‐scale traveling ionospheric disturbances (LSTIDs) were statistically studied using total electron content (TEC) data from the GPS Earth observation network (GEONET) in Japan during 45 months April 1999 to December 2002. One hundred fifty‐four LSTIDs propagating southward identified with time sequences of two‐dimensional TEC maps. Fifty observed 2000, 2001, and 38 Their occurrence rate (occurrence probability one LSTID per 3 hours) increased as Kp value increased, that is, 1% at = 4 75%...
Abstract Using global positioning system (GPS) data taken from 350 dual-frequency GPS receivers in Southern California 2002, we investigated two-dimensional maps of total electron content (TEC) perturbations with a time resolution 30 s and spatial 0.15°×0.15° longitude latitude to reveal statistical characteristics medium-scale traveling ionospheric disturbances (MSTIDs). We found that MSTIDs can be categorized into three types. One type is daytime MSTIDs, which frequently occur winter...
Plasma density structures and associated irregularities in the nighttime midlatitude ionosphere are frequently observed as frontal elongated from northwest to southeast (NW‐SE) Northern Hemisphere. The coupling process between E F regions studied with a three‐dimensional numerical model, which can simulate two instability mechanisms: Perkins ‐region sporadic‐ ( s )‐layer region. fastest growth of coupled occurs when unstable conditions on NW‐SE perturbation satisfied both regions. integrated...
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 other Resolute Bay, Canada (74.7°N, 265.1°E). The Bay incoherent scatter radar observed clear enhancements F region electron density up 10 m −3 within these structures which indicates that are optical manifestations cap patches propagating across cap. this...
[1] This paper introduces a new Earth's atmosphere-ionosphere coupled model that treats seamlessly the neutral atmospheric region from troposphere to thermosphere as well thermosphere-ionosphere interaction including electrodynamics self-consistently. The is especially useful for study of vertical connection between meteorological phenomena and upper behaviors. As an initial simulation using model, we have carried out 30 day consecutive run in September. result reveals longitudinal structure...
Two-dimensional structures of the ionospheric variations generated by acoustic resonance between ground surface and lower thermosphere was observed for first time near epicenter after M 9.0 Tohoku earthquake on March 11, 2011. A short-period oscillation total electron content a GPS receiver array four hours in vicinity epicenter. It centered east where tsunami estimated to commence. The frequency dominant mode 4.5 mHz, 222 seconds period, while there were minor oscillations whose 3.7 mHz 5.3...
Abstract We review measurements of nighttime atmospheric/ionospheric waves in the upper atmosphere Japan, Indonesia, and Australia, using all-sky airglow imagers optical mesosphere thermosphere (OMTIs). The observe two-dimensional patterns emissions from oxygen (wavelength: 557.7 nm) hydroxyl (OH) (near-infrared band) mesopause region (80–100 km) (630.0 thermosphere/ionosphere (200–300 km). Several statistical studies were done to investigate propagation characteristics small-scale (less...
Abstract The equatorial zonal electric field responses to prompt penetration of eastward convection fields (PPEF) were compared at closely spaced longitudinal intervals dusk premidnight sectors during the intense geomagnetic storm 17 March 2015. At sector (Indian longitudes), a rapid uplift F layer >550 km and development plasma bubbles (EPBs) observed. These EPBs found extend up 27.13°N 25.98°S magnetic dip latitudes indicating their altitude ~1670 apex. In contrast, few degrees east in...
The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to mega-electron (MeV). These rotate around Earth longitudinally due gradient curvature of geomagnetic field by co-rotation motion with timescales several tens hours less than 10 min. They interact plasma waves at frequencies mHz kHz mainly equatorial plane magnetosphere, obtain energies up MeV, are lost into ionosphere. In order provide global distribution quantitative evaluation...
Abstract To elucidate the characteristics of electromagnetic conjugacy traveling ionospheric disturbances just after 15 January 2022 Hunga Tonga-Hunga Ha’apai volcanic eruption, we analyze Global Navigation Satellite System-total electron content data and plasma velocity obtained from Super Dual Auroral Radar Network Hokkaido pair radars. Further, use thermal infrared grid with high spatial resolution observed by Himawari 8 satellite to identify lower atmospheric associated surface air...
Abstract An unseasonal equatorial plasma bubble (EPB) event occurred in the East/Southeast Asian sector during geomagnetic storm on 1 December 2023, causing strong amplitude scintillations from to middle latitudes. Based observations multiple instruments over a large latitudinal and longitudinal region, spatial features of super EPB were investigated. The developed vertically at fast rising speed ∼470 m/s magnetic equator extended very high latitude more than 40°N, despite that intensity was...
Abstract Strong Thermal Emission Velocity Enhancement (STEVE) is a latitudinally narrow, purple‐band emission observed at subauroral latitudes. Stable Auroral Red (SAR) arcs characterized by major red emission, and red/green with both green emissions also occur Characteristics of magnetospheric source plasma electromagnetic fields these three types have not been fully understood because the limited conjugate observations between magnetosphere ground. In this study, we report 11 (2 STEVEs, 7...
We have investigated a nighttime medium‐scale traveling ionospheric disturbance (MSTID) observed by an airglow imager at Shigaraki (34.9°N, 25.4°MLAT), Japan, on 17 May 2001. The structure was identified in the images of OI (630.0 nm and 777.4 nm) as NW‐SE band structures (horizontal wavelength: 230 km) moving southwestward with velocity 50 m/s. Neutral wind measured simultaneously from Doppler shift 630.0‐nm emission Fabry‐Perot interferometer Shigaraki. From these parameters, we performed...
We report for the first time large‐scale equatorial F ‐region airglow depletions extending to low‐midlatitudes in both hemispheres. The observational sites were located at low‐midlatitude geomagnetic conjugate points. Clear of 630.0‐nm intensity due plasma bubbles simultaneously observed with two all‐sky imagers Sata, Japan (magnetic latitude 24°N), and its point, Darwin, Australia 22°S), on night November 12, 2001. Airglow depletion regions east‐west scale sizes 40–100 km extend poleward....
By observing the ionospheric F region simultaneously in multiple beams with middle and upper atmosphere radar, we have been able to track passage of gravity waves measure their propagation characteristics. Here develop a climatology wave based on observation 58 daytime experiments conducted during 1986–1994. The thermosphere seems be continuously swept by detectable an incoherent scatter radar. These generally come for hours end from consistent or slowly varying direction, which can any...
Near‐field coseismic perturbations of ionospheric total electron content (TEC), caused by direct acoustic waves from focal regions, can be observed with Global Positioning System (GPS). They appear 10–15 min after the earthquake typical periods ∼4–5 and propagate as fast ∼1 km/s toward directions allowed ambient geomagnetic fields. Ionospheric disturbance, associated 2004 December 26 great Sumatra‐Andaman earthquake, was recorded nine continuous GPS receiving stations in Indonesia Thailand....
Using global positioning system (GPS) data taken from the International GNSS Service (IGS), we investigated total electron content (TEC) perturbations associated with medium‐scale traveling ionospheric disturbances (MSTIDs). We analyzed TEC four or five GPS receivers in each of six regions (Japan, Europe, eastern United States, western Australia, and South America) 3 years (1998, 2000, 2001). To derive perturbation components ( I ′), subtracted 1‐hour running average form time sequence for...