Faculty Profiles - OTSUKA, Yuichi

Papers - OTSUKA, Yuichi

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Multiple-Event Study of Substorm Electric Field Penetration Into Middle Latitudes Based on Simultaneous Observation of 630-nm Airglow Enhancements at Three Stations

Morita, S; Shiokawa, K; Otsuka, Y; Nshitani, N; Shinbori, A; Fujimoto, A; Yoshikawa, A; Nishioka, M; Perwitasari, S; Yamamoto, M; Sori, T

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 10 ) 2025.10

Post-Sunrise Ionospheric Irregularities in Southeast Asia During the Geomagnetic Storm on 19-20 April 2024

Abadi, P; Muafiry, IN; Pratama, TN; Putra, AY; Faturahman, A; Noersomadi; Maryadi, E; Chabibi, FF; Ahmad, UA; Li, GZ; Sun, WJ; Xie, HY; Otsuka, Y; Perwitasari, S; Jamjareegulgran, P

REMOTE SENSING Vol. 17 ( 16 ) 2025.8

High-Resolution GNSS Tomography of Storm-Enhanced Density and Embedded Depletions Over Japan During the May 2024 Super Geomagnetic Storm

Fu, WZ; Otsuka, Y; Ssessanga, N; Yokoyama, T; Yamamoto, M

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 16 ) 2025.8

Reduction of High Latitude Ionospheric Electron Density by the Impact of Negative Solar Wind Pressure Pulse During the Geomagnetic Storm of 23 March 2023

Kakoti, G; Bagiya, MS; Vichare, G; Shiokawa, K; Shreedevi, PR; Nishitani, N; Otsuka, Y; Shinbori, A; Nishioka, M; Perwitasari, S

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 8 ) 2025.8

On the fresh development of midnight plasma bubbles over South America

Vital, LFR; Xu, JY; Otsuka, Y; Ayorinde, TT; Takahashi, H; Barros, D; Carmo, C; Figueiredo, CAOB; Wrasse, CM; Lima, LM; Paulino, I; Wang, C; Li, H; Liu, ZK

EARTH PLANETS AND SPACE Vol. 77 ( 1 ) 2025.8

Characteristics of Nighttime Medium-Scale Traveling Ionospheric Disturbances: Longitudinal Comparison of Their Seasonal and Local Time Variations

Katamzi-Joseph, ZT; Habarulema, JB; Otsuka, Y; Matamba, TM; Nel, AE

SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS Vol. 23 ( 7 ) 2025.7

Causal links to persisting daytime equatorial plasma bubbles over Asia-Pacific region following the geomagnetic storm on 01 December 2023

Rajesh, PK; Lin, CHC; Otsuka, Y; Yamamoto, M; Chen, SP; Lin, CY; Matsuo, T; Nishioka, M; Perwitasari, S; Jin, H; Choi, JM

SCIENTIFIC REPORTS Vol. 15 ( 1 ) 2025.7

Asymmetric Ionospheric Disturbances Observed by GNSS During the 2017 Typhoon Talim and Doksuri: Origin and Characteristics

Fu, JX; Otsuka, Y; Jin, H

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 7 ) 2025.7

Identifying medium-scale traveling ionospheric disturbances driven by atmospheric gravity waves over Japan at sunrise and sunset terminators using high-resolution 3-D GNSS tomography

Fu, WZ; Otsuka, Y; Hocke, K; Ma, GY; Nishioka, M; Jin, H

GPS SOLUTIONS Vol. 29 ( 3 ) 2025.7

A Bootstrapping Convolutional Neural Network Technique for Optimizing Automated Detection of Equatorial Plasma Bubbles by Optical All-Sky Imagers

Okoh, D; Cesaroni, C; Rabiu, B; Shiokawa, K; Otsuka, Y; Ogunjo, S; Akerele, A; Habarulema, JB; Nava, B; Migoya-Orué, Y; Jamjareegulgarn, P; Seun, A; Adama, O; Ochieng, G; Ameh, J; Awuor, A; Baki, P

EARTH AND SPACE SCIENCE Vol. 12 ( 6 ) 2025.6

On the Extraordinary L-Band Scintillation Event Observed in the American Sector During the 23-24 March 2023 Geomagnetic Storm

Socola, JG; Rodrigues, FS; Sousasantos, J; Quesada, MR; Heelis, R; Otsuka, Y; Shinbori, A; Nishioka, M; Perwitasari, S

SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS Vol. 23 ( 6 ) 2025.6

Strong ionospheric activity at the MWA site associated with plasma bubble measured by GNSS

Yoshiura, S; Otsuka, Y; Trott, CM; Null, D; Nishitani, N; Takahashi, K; Nishioka, M; Perwitasari, S; Shinbori, A

PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN Vol. 77 ( 3 ) page： 556 - 561 2025.6

Unveiling the vertical ionospheric responses following the 2024 Noto Peninsula Earthquake with an ultra-dense GNSS network

Fu, WZ; Otsuka, Y; Ssessanga, N; Shinbori, A; Sori, T; Nishioka, M; Perwitasari, S

EARTH PLANETS AND SPACE Vol. 77 ( 1 ) 2025.5

Investigation into the earliest generation of medium-scale traveling ionospheric disturbances with electrodynamic signatures using dense GNSS observations over Japan

Fu, WZ; Otsuka, Y; Yokoyama, T; Li, ZZ; Yamamoto, M; Nishioka, M; Jin, H; Hosokawa, K; Stolle, C

EARTH PLANETS AND SPACE Vol. 77 ( 1 ) 2025.5

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

Guo, X; Zhao, BQ; Yu, TT; Zhang, YL; Otsuka, Y; Shinbori, A; Nishioka, M; Perwitasari, S; Sun, WJ; Hu, LH; Li, GZ; Ren, ZP

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 9 ) 2025.5

Advanced detection methods and machine learning analysis of temporal and spatial patterns of equatorial plasma bubble depth

Adawa, I; Otsuka, Y; Abdelwahab, M; Mahrous, A

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 270 2025.5

Was the Unseasonal Development of Post-Sunset Equatorial Plasma Bubbles in Southeast Asia Driven by Quasi-2-Day Planetary Waves?

Dai, GF; Li, GZ; Otsuka, Y; Hu, LH; Sun, WJ; Ning, BQ; Zhang, DH; Lei, JH; Xie, HY; Zhao, XK; Nishioka, M; Perwitasari, S; Jamjareegulgarn, P; Li, Y; Yan, CX

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 3 ) 2025.3

Responses of the Daytime Low and Equatorial Ionosphere and Thermosphere Over the Indian Region During the Geomagnetic Storm of April 2023

Krishnan, LG; Shiokawa, K; Pant, TK; Lu, G; Shreedevi, PR; Otsuka, Y; Sunda, S

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 3 ) 2025.3

Thank You to Our 2024 Reviewers Open Access

Karnauskas, K; Aiyyer, A; Camargo, S; Capitanio, F; Feakins, S; Fulweiler, R; Ganju, N; Giannini, A; Gu, Y; Huber, C; Ivanov, V; Korte, M; Kumar, S; Lewis, K; Magnusdottir, G; Morlighem, M; Otsuka, Y; Prieto, GA; Qiu, B; Russell, L; Seki, K; Su, H; Sun, DY; Viswanathan, H; Wang, GL; Wang, KC; White, AE; Williams, Q; Zhang, L

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 4 ) 2025.2

Medium-scale traveling ionospheric disturbances created by primary gravity waves generated by a winter storm Open Access

Kogure, M; Chou, MY; Yue, J; Otsuka, Y; Liu, HX; Sassi, F; Pedatella, N; Randall, CE; Harvey, VL

JOURNAL OF SPACE WEATHER AND SPACE CLIMATE Vol. 14 2024.12

Machine learning approach for ionospheric scintillation prediction on ROTI parameter over the African region during solar cycle 24

Tete, S; Otsuka, Y; Zahra, WK; Mahrous, A

ADVANCES IN SPACE RESEARCH Vol. 74 ( 12 ) page： 6325 - 6342 2024.12

Longitudinal Range of the Eastward-Traveling Equatorial Plasma Bubble Inducing Ionospheric Scintillation Reviewed Open Access

Abadi, P; Otsuka, Y; Saito, S; Yamamoto, M; Perwitasari, S; Muafiry, IN; Putra, AY; Faturahman, A

SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS Vol. 22 ( 8 ) 2024.8

High-resolution 3-D imaging of electron density perturbations using ultra-dense GNSS observation networks in Japan: an example of medium-scale traveling ionospheric disturbances Reviewed International coauthorship Open Access

Fu, WZ; Otsuka, Y; Ssessanga, N

EARTH PLANETS AND SPACE Vol. 76 ( 1 ) 2024.7

Leveraging machine learning techniques and GPS measurements for precise TEC rate predictions Reviewed International coauthorship

Tete, S; Otsuka, Y; Zahra, WK; Mahrous, A

GPS SOLUTIONS Vol. 28 ( 3 ) 2024.7

Thank You to Our 2023 Peer Reviewers Reviewed International coauthorship Open Access

Rajaram, H; Aiyyer, A; Camargo, S; Cappa, CD; Dombard, AJ; Donohue, KA; Feakins, S; Flesch, L; Fulweiler, R; Ganju, N; Giannini, A; Gu, Y; Huber, C; Ivanov, V; Karnauskas, K; Korte, M; Lewis, K; Lu, G; Magnusdottir, G; Morlighem, M; Oieroset, M; Otsuka, Y; Prieto, GA; Qiu, B; Russell, L; Su, H; Sun, DY; Wang, GL; Wang, KC; Whalen, C; White, AE; Williams, Q; Yau, A

GEOPHYSICAL RESEARCH LETTERS Vol. 51 ( 9 ) 2024.5

Permulaan Gelembung Plasma Khatulistiwa Semasa Angin Neutral Kuat dan Lemah di Asia Tenggara

Sarudin, I; Hamid, NSA; Abdullah, M; Buhari, SM; Otsuka, Y; Perwitasari, S; Yatini, C

JURNAL KEJURUTERAAN Vol. 36 ( 3 ) page： 1281 - 1289 2024.5

Assessing the potential of ionosonde for forecasting post-sunset equatorial spread F: an observational experiment in Southeast Asia Reviewed International coauthorship Open Access

Abadi, P; Ahmad, UA; Otsuka, Y; Jamjareegulgarn, P; Almahi, A; Perwitasari, S; Supriadi, S; Harjupa, W; Septiawan, RR

EARTH PLANETS AND SPACE Vol. 75 ( 1 ) 2023.12

Equinoctial asymmetry of plasma bubble occurrence and electric field at evening: GPS and ionosonde measurements in Southeast Asia Reviewed

Otsuka, Y; Abadi, P; Hozumi, K; Almahi, A

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 252 2023.11

Daytime Medium Scale Traveling Ionospheric Disturbances (MSTIDS) Over the Andes Mountains at Equatorial and Low Magnetic Latitudes Reviewed International coauthorship Open Access

Figueiredo, CAOB; Wrasse, CM; Vadas, S; Takahashi, H; Otsuka, Y; Nyassor, PK; Shiokawa, K; Paulino, I; Barros, D

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 128 ( 10 ) 2023.10

Responses of the African-European equatorial-, low-, mid-, and high-latitude ionosphere to geomagnetic storms of 2013, 2015 St Patrick's Days, 1 June 2013, and 7 October 2015 Reviewed International coauthorship

Vol. 72 ( 3 ) page： 775 - 789 2023.8

Equatorial plasma bubble intensities across longitudinal sectors of the globe using GNSS observations Reviewed International coauthorship

Vol. 249 2023.8

Statistical Analysis of the Horizontal Phase Velocity Distribution of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances in Airglow Images Over Darwin (12.4°S, 131.0°E)

Tsuboi, T; Shiokawa, K; Otsuka, Y; Fujinami, H; Nakamura, T; Neudegg, D

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 128 ( 8 ) 2023.8

Ionospheric disturbances over South America related to Tonga volcanic eruption Reviewed International coauthorship Open Access

Vol. 75 ( 1 ) 2023.5

Day-to-day variability of the equatorial ionosphere in Asian sector during August-October 2019 Reviewed International coauthorship Open Access

Vol. 10 2023.5

Multi-Event Conjugate Measurements of the SAR Arc Detachment From the Auroral Oval Using DMSP Satellites and an All-Sky Camera at Athabasca, Canada Reviewed International coauthorship

Vol. 128 ( 4 ) 2023.4

Solved and unsolved riddles about low-latitude daytime valley region plasma waves and 150-km echoes Reviewed International coauthorship Open Access

Vol. 10 2023.2

Tandem Observations of Nighttime Mid-Latitude Topside Ionospheric Perturbations Reviewed International coauthorship Open Access

Vol. 21 ( 2 ) 2023.2

Ionospheric Modulation by EMIC Wave-Driven Proton Precipitation: Observations and Simulations Reviewed International coauthorship Open Access

Tian, XB; Yu, YQ; Gong, F; Ma, LX; Cao, JB; Solomon, SC; Shreedevi, PR; Shiokawa, K; Otsuka, Y; Oyama, S; Miyoshi, Y

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 128 ( 1 ) 2023.1

Relationship between geomagnetic storms and occurrence of ionospheric irregularities in the west sector of Africa during the peak of the 24th solar cycle Open Access

Ondede, GO; Rabiu, AB; Okoh, D; Baki, P; Olwendo, J; Shiokawa, K; Otsuka, Y

FRONTIERS IN ASTRONOMY AND SPACE SCIENCES Vol. 9 2022.11

Localized mesospheric ozone destruction corresponding to isolated proton aurora coming from Earth's radiation belt Open Access

Ozaki Mitsunori, Shiokawa Kazuo, Kataoka Ryuho, Mlynczak Martin, Paxton Larry, Connors Martin, Yagitani Satoshi, Hashimoto Shion, Otsuka Yuichi, Nakahira Satoshi, Mann Ian

SCIENTIFIC REPORTS Vol. 12 ( 1 ) 2022.10

Three-Dimensional Fourier Analysis of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances Observed in Airglow Images in Hawaii Over Three Years

Naito Hideto, Shiokawa Kazuo, Otsuka Yuichi, Fujinami Hatsuki, Tsuboi Takuma, Sakanoi Takeshi, Saito Akinori, Nakamura Takuji

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 127 ( 10 ) 2022.10

Statistical Study of Subauroral Arc Detachment at Athabasca, Canada: New Insights on STEVE

Yadav, S; Shiokawa, K; Otsuka, Y; Connors, M

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 127 ( 9 ) 2022.9

Electromagnetic conjugacy of ionospheric disturbances after the 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption as seen in GNSS-TEC and SuperDARN Hokkaido pair of radars observations Open Access

Shinbori Atsuki, Otsuka Yuichi, Sori Takuya, Nishioka Michi, Perwitasari Septi, Tsuda Takuo, Nishitani Nozomu

EARTH PLANETS AND SPACE Vol. 74 ( 1 ) 2022.7

Modeling Post-Sunset Equatorial Spread-F Occurrence as a Function of Evening Upward Plasma Drift Using Logistic Regression, Deduced from Ionosondes in Southeast Asia Open Access

Abadi, P; Ahmad, UA; Otsuka, Y; Jamjareegulgarn, P; Martiningrum, DR; Faturahman, A; Perwitasari, S; Saputra, RE; Septiawan, RR

REMOTE SENSING Vol. 14 ( 8 ) 2022.4

Variations of Zonal Wind Velocity in the Thermosphere Observed at Southeast Asian Sector During Quiet and Active Geomagnetic Days

Sarudin, I; Hamid, NSA; Abdullah, M; Rusli, FNSM; Otsuka, Y; Shiokawa, K; Yatini, C; Komonjinda, S; Somboon, E

JURNAL FIZIK MALAYSIA Vol. 43 ( 1 ) page： 10025 - 10035 2022

Xtend, the Soft X-ray Imaging Telescope for the X-ray Imaging and Spectroscopy Mission (XRISM) Open Access

Mori, K; Tomida, H; Nakajima, H; Okajima, T; Noda, H; Tanaka, T; Uchida, H; Hagino, K; Kobayashi, SB; Suzuki, H; Yoshida, T; Murakami, H; Uchiyama, H; Nobukawa, M; Nobukawa, KK; Yoneyama, T; Matsumoto, H; Tsuru, TG; Yamauchi, M; Hatsukade, I; Ishida, M; Maeda, Y; Hayashi, T; Tamura, K; Boissay-Malaquin, R; Sato, T; Hiraga, J; Kohmura, T; Yamaoka, K; Dotani, T; Ozaki, M; Tsunemi, H; Kanemaru, Y; Sato, J; Takaki, T; Terada, Y; Miyazaki, K; Kusunoki, K; Otsuka, Y; Yokosu, H; Yonemaru, W; Asahina, Y; Asakura, K; Yoshimoto, M; Ode, Y; Sato, J; Hakamata, T; Aoyagi, M; Aoki, Y; Tsunomachi, S; Doi, T; Aoki, D; Fujisawa, K; Kitajima, M; Hayashida, K

SPACE TELESCOPES AND INSTRUMENTATION 2022: ULTRAVIOLET TO GAMMA RAY Vol. 12181 2022

ROLES OF EVENING EASTWARD NEUTRAL WIND AND EQUATORIAL ELECTROJET ON PRE-REVERSAL ENHANCEMENT INFERRED FROM GOCE SATELLITE AND GROUND-BASED OBSERVATIONS Open Access

Abadi, P; Otsuka, Y; Liu, HX; Hozumi, K; Martiningrum, DR

18TH ANNUAL MEETING OF THE ASIA OCEANIA GEOSCIENCES SOCIETY, AOGS 2021 page： 218 - 220 2022

An experimental investigation into the possible connections between the zonal neutral wind speeds and equatorial plasma bubble drift velocities over the African equatorial region Open Access

Okoh, DI; Rabiu, AB; Shiokawa, K; Otsuka, Y; Wu, Q; Seemala, GK; Katamzi-Joseph, ZT

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 220 2021.9

Preface to the Special Issue on recent advances in the study of Equatorial Plasma Bubbles and Ionospheric Scintillation Open Access

Otsuka, Y; Spogli, L; Ram, ST; Li, GZ

EARTH AND PLANETARY PHYSICS Vol. 5 ( 5 ) page： 365 - 367 2021.9

L-Band Synthetic Aperture Radar Observation of Ionospheric Density Irregularities at Equatorial Plasma Depletion Region Open Access

Sato, H; Kim, JS; Otsuka, Y; Wrasse, CM; de Paula, ER; de Souza, JR

GEOPHYSICAL RESEARCH LETTERS Vol. 48 ( 16 ) 2021.8

Characteristics of Medium-Scale Traveling Ionospheric Disturbances and Ionospheric Irregularities at Mid-Latitudes Revealed by the Total Electron Content Associated With the Beidou Geostationary Satellite

Huang, F; Lei, J; Otsuka, Y; Luan, X; Liu, Y; Zhong, J; Dou, X

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING Vol. 59 ( 8 ) page： 6424 - 6430 2021.8

Statistical study of medium-scale traveling ionospheric disturbances in low-latitude ionosphere using an automatic algorithm Open Access

Cheng, PH; Lin, C; Otsuka, Y; Liu, HL; Rajesh, PK; Chen, CH; Lin, JT; Chang, MT

EARTH PLANETS AND SPACE Vol. 73 ( 1 ) 2021.5

Medium-Scale Traveling Ionospheric Disturbances

Otsuka, Y

IONOSPHERE DYNAMICS AND APPLICATIONS Vol. 260 page： 421 - 437 2021

Equatorial Plasma Bubble Occurrence Under Propagation of MSTID and MLT Gravity Waves Open Access

Takahashi, H; Wrasse, CM; Figueiredo, CAOB; Barros, D; Paulino, I; Essien, P; Abdu, MA; Otsuka, Y; Shiokawa, K

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 125 ( 9 ) 2020.9

Temporal and Spatial Variations of Total Electron Content Enhancements During a Geomagnetic Storm on 27 and 28 September 2017 Open Access

Shinbori, A; Otsuka, Y; Sori, T; Tsugawa, T; Nishioka, M

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 125 ( 7 ) 2020.7

Equatorial Plasma Bubble Zonal Drift Velocity Variations in Response to Season, Local Time, and Solar Activity across Southeast Asia

Sarudin, I; Hamid, NSA; Abdullah, M; Buhari, SM; Shiokawa, K; Otsuka, Y; Yatini, CY

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 125 ( 3 ) 2020.3

Multievent Analysis of Oscillatory Motion of Medium-Scale Traveling Ionospheric Disturbances Observed by a 630-nm Airglow Imager Over Tromso Open Access

Yadav, S; Shiokawa, K; Oyama, S; Otsuka, Y

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 125 ( 3 ) 2020.3

Wavenumber Spectra of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances Based on More Than 10-Year Airglow Images in Japan, Russia, and Canada Open Access

Satoshi Tsuchiya, Kazuo Shiokawa, Yuichi Otsuka, Takuji Nakamura, Mamoru Yamamoto, Martin Connors, Ian Schofield, Boris Shevtsov, Igor Poddelsky

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 125 ( 3 ) 2020.3

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

We have studied atmospheric gravity waves (AGWs) and nighttime medium-scale traveling ionospheric disturbances (MSTIDs) by applying three-dimensional spectral analysis technique to 557.7- and 630.0-nm airglow images at Shigaraki (SGK) (35 degrees N, 136 degrees E, 1999-2017) and Rikubetsu (RIK) (44 degrees N, 144 degrees E, 1999-2017), Japan, Athabasca (ATH), Canada, (55 degrees N, 247 degrees E, 2005-2017), and Magadan (MGD), Russia (60 degrees N, 151 degrees E, 2008-2017), focusing on their horizontal wavenumber spectra. For the AGWs in 557.7-nm images, the power spectra in summer are stronger than in other seasons, probably due to stronger tropospheric convection. The highest energy content of the waves are mostly at wavelengths between 20 and 300 km at MGD, ATH, and RIK, while it is above 200 km at SGK. The largest power spectral density is obtained at RIK at wavelengths of 30-100 km and then ATH. The slopes of the horizontal wavenumber spectra varies from -2.77 to -3.22. From the MSTIDs in 630.0-nm images, the power spectra in summer at RIK and SGK are stronger than those in other seasons regardless of solar activity. The power spectra in solar quiet time are stronger than those in solar active time at all four stations. These features can be explained by the Perkins instability with coupling between sporadic E and F layers. The spectral slope decreases with increasing latitudes. Weak positive correlations were obtained between the daily wave power of AGWs in 557.7-nm images and MSTIDs in 630.0-nm images, suggesting that the MSTIDs in the thermosphere may be partially generated by the AGWs from the mesopause region.Plain Language Summary In this paper we study atmospheric gravity waves (AGWs) and nighttime medium-scale traveling ionospheric disturbances (MSTIDs) observed at four stations in Japan, Canada, and Russia, in 557.7- and 630.0-nm airglow images over more than 10 years. The 557.7-nm airglow has an emission layer at altitudes of 90-100 km (mesopause region). The waves seen in the 557.7-nm airglow images mainly indicates AGWs. The 630.0-nm airglow has an emission layer at altitudes of 200-300 km (bottomside ionosphere). The waves seen in the 630.0-nm airglow images mainly indicates MSTIDs in the ionosphere. The AGWs in the mesopause region are the main driver of global atmospheric circulation in the middle atmosphere. The MSTIDs in the bottomside ionosphere are one of the causes of the satellite positioning error. We show typical energy content, propagation direction, and wavelengths of these waves at these two altitudes and discuss possible reason of the observed characteristics. These results contribute to our understanding of generation and propagation of AGWs and MSTIDs in the upper atmosphere.

<OTSUKA, Yuichi>

Papers - OTSUKA, Yuichi