, Part-time Lecturer, 2021.05 - 2023.03

Tohoku University, Guest researcher, 2024.04 -

Yamagata University, Lecturer, 2024.04 -

Overview of the LAPYUTA mission (Life-environmentology, Astronomy, and PlanetarY Ultraviolet Telescope Assembly), Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 18, 2024.08

Fuminori Tsuchiya, Go Murakami, Atsushi Yamazaki, Shingo Kameda, Tomoki Kimura, Ryoichi Koga, Kei Masunaga, Shotaro Sakai, Masahiro Ikoma, Akifumi Nakayama, Masami Ouchi, Masaomi Tanaka, Shin Toriumi,...

Single Author

A Technique for Retrieving the Exospheric Number Density Distribution from Pickup Ion Ring Distributions, The Planetary Science Journal, 5(8) 180, 2024.08

Kei Masunaga, Naoki Terada, François Leblanc, Yuki Harada, Takuya Hara, Shotaro Sakai, Shoichiro Yokota, Kanako Seki, Atsushi Yamazaki, James. P. McFadden, Tomohiro Usui

Single Author

On the Periodic Variation of the Ion Density in the Martian Dayside Ionosphere During the Regional Dust Storm in September 2016, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 129(4) , 2024.04

Hara, T; Masunaga, K; Terada, N; Sakai, S; Osanai, T; Seki, K; Fowler, CM; Hanley, KG; McFadden, JP; Curry, SM

Single Author

BepiColombo mission confirms stagnation region of Venus and reveals its large extent, Nature Communications, 13(1) , 2022.12

M. Persson, S. Aizawa, N. André, S. Barabash, Y. Saito, Y. Harada, D. Heyner, S. Orsini, A. Fedorov, C. Mazelle, Y. Futaana, L. Z. Hadid, M. Volwerk, G. Collinson, B. Sanchez-Cano, A. Barthe, E. Penou...

Single Author

Alternate oscillations of Martian hydrogen and oxygen upper atmospheres during a major dust storm., Nature communications, 13(1) 6609, 2022.11

Kei Masunaga, Naoki Terada, Nao Yoshida, Yuki Nakamura, Takeshi Kuroda, Kazuo Yoshioka, Yudai Suzuki, Hiromu Nakagawa, Tomoki Kimura, Fuminori Tsuchiya, Go Murakami, Atsushi Yamazaki, Tomohiro Usui, I...

Single Author

Reflectivity of Venus’s Dayside Disk During the 2020 Observation Campaign: Outcomes and Future Perspectives, The Planetary Science Journal, 3(9) 209, 2022.09

Yeon Joo Lee, Antonio García Muñoz, Atsushi Yamazaki, Eric Quémerais, Stefano Mottola, Stephan Hellmich, Thomas Granzer, Gilles Bergond, Martin Roth, Eulalia Gallego-Cano, Jean-Yves Chaufray, Rozenn R...

Single Author

In Situ Observation of Solar-flare-induced Proton Cyclotron Waves Upstream from Mars, Astrophysical Journal, 934(2) , 2022.08

Haibo Lin, Jianpeng Guo, Kei Masunaga, Kanako Seki, Christian Mazelle, Dan Zhao, Hui Huang, Juan Zhao, Yong Wei, Libo Liu

Single Author

Seasonal and Dust‐Related Variations in the Dayside Thermospheric and Ionospheric Compositions of Mars Observed by MAVEN/NGIMS, Journal of Geophysical Research: Planets, 126(11) , 2021.11

Nao Yoshida, Naoki Terada, Hiromu Nakagawa, David A. Brain, Shotaro Sakai, Yuki Nakamura, Mehdi Benna, Kei Masunaga

Single Author

Flow directions of low-energy ions in and around the diamagnetic cavity of comet 67P, Monthly Notices of the Royal Astronomical Society, 507(4) 4900-4913, 2021.09

Sofia Bergman, Gabriella Stenberg~Wieser, Martin Wieser, Hans Nilsson, Erik Vigren, Arnaud Beth, Kei Masunaga, Anders Eriksson

Single Author

Global Venus-Solar Wind Coupling and Oxygen Ion Escape, Geophysical Research Letters, 48(3) , 2021

Persson, M., Futaana, Y., Ramstad, R., Schillings, A., Masunaga, K., Nilsson, H., Fedorov, A., Barabash, S.

Single Author

Vertical Coupling Between the Cloud-Level Atmosphere and the Thermosphere of Venus Inferred From the Simultaneous Observations by Hisaki and Akatsuki, Journal of Geophysical Research: Planets, 125(3) , 2020

Nara, Y., Imamura, T., Masunaga, K., Lee, Y.J., Terada, N., Yoshioka, K., Yamazaki, A., Seki, K., Yoshikawa, I., Yamada, M., Watanabe, S.

Single Author

The Venusian Atmospheric Oxygen Ion Escape: Extrapolation to the Early Solar System, Journal of Geophysical Research: Planets, 125(3) , 2020

Persson, M., Futaana, Y., Ramstad, R., Masunaga, K., Nilsson, H., Hamrin, M., Fedorov, A., Barabash, S.

Single Author

Martian Oxygen and Hydrogen Upper Atmospheres Responding to Solar and Dust Storm Drivers: Hisaki Space Telescope Observations, Journal of Geophysical Research: Planets, 125(12) , 2020

Masunaga, K., Yoshioka, K., Chaffin, M.S., Deighan, J., Jain, S.K., Schneider, N.M., Kimura, T., Tsuchiya, F., Murakami, G., Yamazaki, A., Terada, N., Yoshikawa, I.

Single Author

Flow pattern of accelerated cometary ions inside and outside the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko, A&A, 630 , 2019

{Masunaga, K.}, {Nilsson, H.}, {Behar, E.}, {Stenberg Wieser, G.}, {Wieser, M.}, {Goetz, C.}

Single Author

Effects of the solar wind and the solar EUV flux on O⁺ escape rates from Venus, Icarus, 321 379-387, 2019

Masunaga, K., Futaana, Y., Persson, M., Barabash, S., Zhang, T.L., Rong, Z.J., Fedorov, A.

Single Author

Statistical Study of Relations Between the Induced Magnetosphere, Ion Composition, and Pressure Balance Boundaries Around Mars Based On MAVEN Observations, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 122(9) 9723-9737, 2017.09

Matsunaga, K; Seki, K; Brain, DA; Hara, T; Masunaga, K; Mcfadden, JP; Halekas, JS; Mitchell, DL; Mazelle, C; Espley, JR; Gruesbeck, J; Jakosky, BM

Single Author

Dawn-dusk difference of periodic oxygen EUV dayglow variations at Venus observed by Hisaki, ICARUS, 292 102-110, 2017.08

Masunaga, K; Seki, K; Terada, N; Tsuchiya, F; Kimura, T; Yoshioka, K; Murakami, G; Yamazaki, A; Tao, C; Leblanc, F; Yoshikawa, I

Single Author

Statistical analysis of the reflection of incident O<SUP>+</SUP> pickup ions at Mars: MAVEN observations, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 122(4) 4089-4101, 2017.04

Masunaga, K; Seki, K; Brain, DA; Fang, X; Dong, Y; Jakosky, BM; McFadden, JP; Halekas, JS; Connerney, JEP; Mitchell, DL; Eparvier, FG

Single Author

The Mars crustal magnetic field control of plasma boundary locations and atmospheric loss: MHD prediction and comparison with MAVEN, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 122(4) 4117-4137, 2017.04

Fang, XH; Ma, YJ; Masunaga, K; Dong, YX; Brain, D; Halekas, J; Lillis, R; Jakosky, B; Connerney, J; Grebowsky, J; Dong, CF

Single Author

O<SUP>+</SUP> ion beams reflected below the Martian bow shock: MAVEN observations, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 121(4) 3093-3107, 2016.04

Masunaga, K; Seki, K; Brain, DA; Fang, X; Dong, Y; Jakosky, BM; McFadden, JP; Halekas, JS; Connerney, JEP

Single Author

Periodic variations of oxygen EUV dayglow in the upper atmosphere of Venus: Hisaki/EXCEED observations, JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, 120(12) 2037-2052, 2015.12

Masunaga, K; Seki, K; Terada, N; Tsuchiya, F; Kimura, T; Yoshioka, K; Murakami, G; Yamazaki, A; Kagitani, M; Tao, C; Fedorov, A; Futaana, Y; Zhang, TL; Shiota, D; Leblanc, F; Chaufray, JY; Yoshikawa, ...

Single Author

The extension of ionospheric holes into the tail of Venus, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 119(8) , 2014.08

Collinson, GA; Fedorov, A; Futaana, Y; Masunaga, K; Hartle, R; Stenberg, G; Grebowsky, J; Holmström, M; Andre, N; Barabash, S; Zhang, TL

Single Author

Inner heliosphere MHD modeling system applicable to space weather forecasting for the other planets, SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, 12(4) 187-204, 2014.04

Shiota, D; Kataoka, R; Miyoshi, Y; Hara, T; Tao, C; Masunaga, K; Futaana, Y; Terada, N

Single Author

Dependence of O<SUP>+</SUP> escape rate from the Venusian upper atmosphere on IMF directions, GEOPHYSICAL RESEARCH LETTERS, 40(9) 1682-1685, 2013.05

Masunaga, K; Futaana, Y; Stenberg, G; Barabash, S; Zhang, TL; Fedorov, A; Okano, S; Terada, N

Single Author

O<SUP>+</SUP> outflow channels around Venus controlled by directions of the interplanetary magnetic field: Observations of high energy O<SUP>+</SUP> ions around the terminator, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 116 , 2011.09

Masunaga, K; Futaana, Y; Yamauchi, M; Barabash, S; Zhang, TL; Fedorov, AO; Terada, N; Okano, S

Single Author