Yuichi Otsuka
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View article: Simultaneous Observations of Quasi‐Orthogonal Nighttime MSTIDs at Conjugate African‐European Midlatitude Stations on 4 October 2018
Simultaneous Observations of Quasi‐Orthogonal Nighttime MSTIDs at Conjugate African‐European Midlatitude Stations on 4 October 2018 Open
Two quasi‐orthogonal nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) were observed by conjugate midlatitude all‐sky imagers in Sutherland (32.4S, 20.8E; magnetic latitude: −40.9) and Asiago (45.87N, 11.53E; magnetic lati…
View article: Unusual Phase Alignment of Nighttime Electrified Medium‐Scale Traveling Ionospheric Disturbance After Moderate Geomagnetic Storms and Response to Substorms
Unusual Phase Alignment of Nighttime Electrified Medium‐Scale Traveling Ionospheric Disturbance After Moderate Geomagnetic Storms and Response to Substorms Open
A nighttime electrified medium‐scale traveling ionospheric disturbance (EMSTID) was observed over Japan on 17 March 2003, after two moderate geomagnetic storms. Unlike typical northwest‐southeast alignment in quiet conditions, the EMSTID e…
View article: Multiple‐Event Study of Substorm Electric Field Penetration Into Middle Latitudes Based on Simultaneous Observation of 630‐nm Airglow Enhancements at Three Stations
Multiple‐Event Study of Substorm Electric Field Penetration Into Middle Latitudes Based on Simultaneous Observation of 630‐nm Airglow Enhancements at Three Stations Open
It is known that convection electric fields develop in the polar region associated with substorm onset, and a westward electric field penetrates to lower latitudes on the night side. Two‐dimensional observations of 630‐nm airglow enhanceme…
View article: Post-Sunrise Ionospheric Irregularities in Southeast Asia During the Geomagnetic Storm on 19–20 April 2024
Post-Sunrise Ionospheric Irregularities in Southeast Asia During the Geomagnetic Storm on 19–20 April 2024 Open
We present new insights into post-sunrise ionospheric irregularities in Southeast Asia during the intense geomagnetic storm of 19–20 April 2024. By utilizing Total Electron Content (TEC) and Rate of TEC Change Index (ROTI) maps, along with…
View article: High‐Resolution GNSS Tomography of Storm‐Enhanced Density and Embedded Depletions Over Japan During the May 2024 Super Geomagnetic Storm
High‐Resolution GNSS Tomography of Storm‐Enhanced Density and Embedded Depletions Over Japan During the May 2024 Super Geomagnetic Storm Open
The Asian sector is reported to have experienced a strong electron density enhancement during the May 2024 super geomagnetic storm between local evening and sunrise. We present a high‐resolution 3‐D ionospheric reconstructions over Japan u…
View article: Reduction of High Latitude Ionospheric Electron Density by the Impact of Negative Solar Wind Pressure Pulse During the Geomagnetic Storm of 23 March 2023
Reduction of High Latitude Ionospheric Electron Density by the Impact of Negative Solar Wind Pressure Pulse During the Geomagnetic Storm of 23 March 2023 Open
The G3‐G4 class geomagnetic storm on 23 March 2023, triggered by an unexpected coronal mass ejection (CME), caused a sudden solar wind dynamic pressure drop (SWDPD) event with a substantial drop of more than 15 nPa. This large pressure dro…
View article: Characteristics of Nighttime Medium‐Scale Traveling Ionospheric Disturbances: Longitudinal Comparison of Their Seasonal and Local Time Variations
Characteristics of Nighttime Medium‐Scale Traveling Ionospheric Disturbances: Longitudinal Comparison of Their Seasonal and Local Time Variations Open
This study presents a statistical analysis of the occurrence rate of midlatitude nighttime medium scale traveling ionospheric disturbances (MSTIDs) that were detected in Swarm plasma density measurements from 2014 to 2023. Monthly and loca…
View article: Asymmetric Ionospheric Disturbances Observed by GNSS During the 2017 Typhoon Talim and Doksuri: Origin and Characteristics
Asymmetric Ionospheric Disturbances Observed by GNSS During the 2017 Typhoon Talim and Doksuri: Origin and Characteristics Open
The influence of typhoons on the ionosphere has been mentioned in many studies, while the relationship and coupling processes remain elusive. Here, we report findings on concentric ionospheric disturbance (CIDs) during typhoon Talim and Do…
View article: Characteristics of temporal and spatial variation of the electron density in the plasmasphere and ionosphere during the May 2024 super geomagnetic storm
Characteristics of temporal and spatial variation of the electron density in the plasmasphere and ionosphere during the May 2024 super geomagnetic storm Open
The spatial distribution of electron density in the ionosphere exhibits notable variability and undergoes considerable changes during storms and substorms driven by solar wind disturbances. Electron density variations and irregularities ca…
View article: A Bootstrapping Convolutional Neural Network Technique for Optimizing Automated Detection of Equatorial Plasma Bubbles by Optical All‐Sky Imagers
A Bootstrapping Convolutional Neural Network Technique for Optimizing Automated Detection of Equatorial Plasma Bubbles by Optical All‐Sky Imagers Open
Equatorial plasma bubbles (EPBs) disrupt satellite‐based communication and navigation systems, particularly in equatorial regions. Reliable detection and classification of EPBs from all‐sky imager (ASI) images are essential for accurate sp…
View article: On the Extraordinary L‐Band Scintillation Event Observed in the American Sector During the 23–24 March 2023 Geomagnetic Storm
On the Extraordinary L‐Band Scintillation Event Observed in the American Sector During the 23–24 March 2023 Geomagnetic Storm Open
We report an extraordinary L‐band scintillation event detected in the American sector on the night of 23–24 March 2023. The event was detected using observations distributed from the magnetic equator to mid latitudes. The observations were…
View article: Insights into Conjugate Hemispheric Ionospheric Disturbances Associated with the Beirut Port Explosion on 4 August 2020 Using Multi Low-Earth-Orbit Satellites
Insights into Conjugate Hemispheric Ionospheric Disturbances Associated with the Beirut Port Explosion on 4 August 2020 Using Multi Low-Earth-Orbit Satellites Open
In this study, we analysed remote sensing data collected during the Beirut port explosion on 4 August 2020 at 15.08 UT. For this purpose, we selected three Low-Earth-Orbit (LEO) satellite missions that passed near the Beirut port explosion…
View article: A Peculiar Discontinuous Ionospheric Latitudinal Variation Over the East Asia Region During the Recovery Phase of the November 2003 Super Magnetic Storm: A Hint From May 2024 Superstorm
A Peculiar Discontinuous Ionospheric Latitudinal Variation Over the East Asia Region During the Recovery Phase of the November 2003 Super Magnetic Storm: A Hint From May 2024 Superstorm Open
In this study, we analyze a discontinuous negative storm evolution process in the ionosphere over the East Asian region during the recovery phase of the geomagnetic storms on 20 and 21 November 2003, using data from the Global Ultraviolet …
View article: Was the Unseasonal Development of Post‐Sunset Equatorial Plasma Bubbles in Southeast Asia Driven by Quasi‐2‐Day Planetary Waves?
Was the Unseasonal Development of Post‐Sunset Equatorial Plasma Bubbles in Southeast Asia Driven by Quasi‐2‐Day Planetary Waves? Open
Previous studies suggest that the planetary waves in mesosphere and low thermosphere (MLT) could modulate the occurrence of equatorial plasma bubbles (EPBs) via altering post‐sunset F layer height. Using simultaneous observations by Global…
View article: Coincident/Simultaneous Observations of Stratospheric Concentric Gravity Waves and Concentric Traveling Ionospheric Disturbances Over the Continental U.S. in 2022
Coincident/Simultaneous Observations of Stratospheric Concentric Gravity Waves and Concentric Traveling Ionospheric Disturbances Over the Continental U.S. in 2022 Open
This study examines the seasonal distributions of simultaneous stratospheric concentric gravity waves (GWs) observed by the Atmospheric Infrared Sounders and concentric traveling ionospheric disturbances (TIDs) detected by the ground‐based…
View article: Thank You to Our 2024 Reviewers
Thank You to Our 2024 Reviewers Open
On behalf of the journal, AGU, and the scientific community, the editors of Geophysical Research Letters would like to sincerely thank those who reviewed manuscripts in 2024. The hours reading and commenting on manuscripts not only improve…
View article: Monitoring of Ionospheric Variability Using the Low lAtitude Long Range Ionospheric raDar (LARID): Capabilities, Advantages and Limitations
Monitoring of Ionospheric Variability Using the Low lAtitude Long Range Ionospheric raDar (LARID): Capabilities, Advantages and Limitations Open
A Low lAtitude long Range Ionospheric raDar (LARID), which was built recently at Dongfang (19.2°N, 108.8°E, magnetic latitude 13.9°), Hainan Is., China, is employed to study the ionospheric variability over a large region. The LARID consis…
View article: Midlatitude Plasma Blob‐like Structures Along With Super Equatorial Plasma Bubbles During the May 2024 Great Geomagnetic Storm
Midlatitude Plasma Blob‐like Structures Along With Super Equatorial Plasma Bubbles During the May 2024 Great Geomagnetic Storm Open
Plasma blob is generally a low‐latitude phenomenon occurring at the poleward edge of equatorial plasma bubble (EPB) during post‐sunset periods. Here we report a case of midlatitude ionospheric plasma blob‐like structures occurring along wi…
View article: X‐Raying Neutral Density Disturbances in the Mesosphere and Lower Thermosphere Induced by the 2022 Hunga‐Tonga Volcano Eruption‐Explosion
X‐Raying Neutral Density Disturbances in the Mesosphere and Lower Thermosphere Induced by the 2022 Hunga‐Tonga Volcano Eruption‐Explosion Open
We present X‐ray observations of the upper atmospheric density disturbance caused by the explosive eruption of the Hunga Tonga‐Hunga Ha'apai (HTHH) volcano on 15 January 2022. From 14 January to 16 January, the Chinese X‐ray astronomy sate…
View article: X-Raying Neutral Density Disturbances in the Mesosphere and Lower Thermosphere induced by the 2022 Hunga-Tonga Volcano Eruption-Explosion
X-Raying Neutral Density Disturbances in the Mesosphere and Lower Thermosphere induced by the 2022 Hunga-Tonga Volcano Eruption-Explosion Open
We present X-ray observations of the upper atmospheric density disturbance caused by the explosive eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano on 15 January 2022. From 14 January to 16 January, the Chinese X-ray astronomy sate…
View article: Longitudinal Range of the Eastward‐Traveling Equatorial Plasma Bubble Inducing Ionospheric Scintillation
Longitudinal Range of the Eastward‐Traveling Equatorial Plasma Bubble Inducing Ionospheric Scintillation Open
Equatorial Plasma Bubbles (EPBs) can generate ionospheric scintillation at GHz frequencies used in the Global Navigation Satellite System (GNSS). Emerging at any longitude following sunset and typically moving eastward, monitoring the EPBs…
View article: Solar activity dependence for the relationship between nighttime medium-scale traveling ionospheric disturbance and sporadic E (Es) layer activities in summer during 1998–2019 over Japan
Solar activity dependence for the relationship between nighttime medium-scale traveling ionospheric disturbance and sporadic E (Es) layer activities in summer during 1998–2019 over Japan Open
To investigate solar activity dependence of the coupling between medium-scale traveling ionosphere disturbance (MSTID) and sporadic E ( Es ) layer, we analyzed the total electron content (TEC) obtained from a Japanese global positioning sy…
View article: Regional Ionospheric Super Bubble Induced by Significant Upward Plasma Drift During the 1 December 2023 Geomagnetic Storm
Regional Ionospheric Super Bubble Induced by Significant Upward Plasma Drift During the 1 December 2023 Geomagnetic Storm Open
An unseasonal equatorial plasma bubble (EPB) event occurred in the East/Southeast Asian sector during the geomagnetic storm on 1 December 2023, causing strong amplitude scintillations from equatorial to middle latitudes. Based on the obser…