Faculty Profiles - OYAMA, Shin-ichiro

Papers - OYAMA, Shin-ichiro

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Lower thermospheric wind variations in auroral patches during the substorm recovery phase Reviewed Open Access

Shin-ichiro Oyama, Kazuo Shiokawa, Yoshizumi Miyoshi, Keisuke Hosokawa, Brenton J. Watkins, Junichi Kurihara, Takuo T. Tsuda andChristopher T. Fallen

J. Geophys. Res., Space Physics Vol. 121 ( 4 ) page： 3564-3577 2016.5

Relation between fine structure of energy spectra for pulsating aurora electrons and frequency spectra of whistler mode chorus waves Reviewed Open Access

Miyoshi, Y., S. Saito, K. Seki, T. Nishiyama, R. Kataoka, K. Asamura, Y. Katoh, Y. Ebihara, T. Sakanoi, M. Hirahara, S. Oyama, S. Kurita, and O. Santolik

J. Geophys. Res. Space Physics 2015.8

A case study on generation mechanisms of a sporadic sodium layer above Tromsoe (69.6N) during a night of high auroral activity Reviewed Open Access

Takahashi, T., Nozawa, S., Tsuda, T. T., Ogawa, Y., Saito, N., Hidemori, T., Kawahara, T. D., Hall, C., Fujiwara, H., Matuura, N., Brekke, A., Tsutsumi, M., Wada, S., Kawabata, T., Oyama, S., and Fujii, R

Ann. Geophys. 2015.8

Statistical study of auroral fragmentation into patches Reviewed Open Access

Hashimoto, A., K. Shiokawa, Y. Otsuka, S.-i. Oyama, S. Nozawa, T. Hori, M. Lester, and M. G. Johnsen

J. Geophys. Res. Space Physics 2015.7

Energetic electron precipitation associated with pulsating aurora: EISCAT and Van Allen Probe observations Reviewed Open Access

Miyoshi, Y., S. Oyama, S. Saito, S. Kurita, H. Fujiwara, R. Kataoka, Y. Ebihara, C. Kletzing, G. Reeves, O. Santolik, M. Cliverd, C. J. Rodger, E. Turunen, and F. Tsuchiya

J. Geophys. Res. Space Physics 2015.3

Approximate forms of daytime ionospheric conductance Reviewed Open Access

Ieda, A., S. Oyama, H. Vanhamäki, R. Fujii, A. Nakamizo, O. Amm, T. Hori, M. Takeda, G. Ueno, A. Yoshikawa, R. J. Redmon, W. F. Denig, Y. Kamide, and N. Nishitani

J. Geophys. Res. Space Physics 2014.11

A case study of gravity wave dissipation in the polar MLT region using sodium LIDAR and radar data Reviewed Open Access

Takahashi, T., S. Nozawa, M. Tsutsumi, C. Hall, S. Suzuki, T. T. Tsuda, T. D. Kawahara, N. Saito, S. Oyama, S. Wada, T. Kawabata, H. Fujiwara, A. Brekke, A. Manson, C. Meek, and R. Fujii

Ann. Geophys. 2014.10

Auroral fragmentation into patches Reviewed

Shiokawa, K., A. Hashimoto, T. Hori, K. Sakaguchi, Y. Ogawa, E. Donovan, E. Spanswick, M. Connors, Y. Otsuka, S. Oyama, S. Nozawa, and K. McWilliams

J. Geophys. Res. Space Physics 2014.9

Height‐dependent ionospheric variations in the vicinity of nightside poleward expanding aurora after substorm onset Reviewed Open Access

Oyama, S., Y. Miyoshi, K. Shiokawa, J. Kurihara, T. T. Tsuda, and B. J. Watkins

Vol. 119 2014.5

Decrease in sodium density observed during auroral particle precipitation over Tromsoe, Norway Reviewed Open Access

Tsuda, T., S. Nozawa, T. D. Kawahara, T. Kawabata, N. Saito, S. Wada, Y. Ogawa, S. Oyama, C. M. Hall, M. Tsutsumi, M. K. Ejiri, S. Suzuki, T. Takahashi, T. Nakamura

Geophys. Res. Let. 2013.8

Observation of nighttime medium-scale travelling ionospheric disturbances by two 630-nm airglow imagers near the auroral zone Reviewed

Shiokawa, K., M. Mori, Y. Otsuka, S. Oyama, S. Nozawa, S. Suzuki, and M. Connors

J. Atmos. Solar-Terr. Phys. 2013.4

Estimation of the layered ionospheric conductance using data from a multi-wavelength photometer at the European Incoherent Scatter (EISCAT) radar site Reviewed

Oyama, S., T. Watanabe, R. Fujii, S. Nozawa1, and T. T. Tsuda

Antarctic Record Vol. 57 ( 3 ) page： 339-356 2013

Development of low-cost sky-scanning Fabry-Perot interferometers for airglow and auroral studies Reviewed Open Access

Shiokawa, K., Y. Otsuka, S. Oyama, S. Nozawa, M. Satoh, Y. Katoh, Y. Hamaguchi, Y. Yamamoto, and J. Meriwether

Earth Planets Space 2012.11

Motion of high-latitude nighttime medium-scale traveling ionospheric disturbances associated with auroral brightening Reviewed Open Access

Shiokawa, K., M. Mori, Y. Otsuka, S. Oyama, and S. Nozawa

J. Geophys. Res. 2012.10

Mean winds, tides, and quasi-2 day waves above Bear Island Reviewed

Nozawa, S., C. M. Hall, M. Tsutsumi, A. Brekke, Y. Ogawa, T. T. Tsuda, S. Oyama, and R. Fujii

J. Atmos. Solar-Terr. Phys. 2012.5

Temporal variations of the ion-neutral collision frequency from EISCAT observations in the polar lower ionosphere during periods of geomagnetic disturbances Reviewed Open Access

Oyama, S., J. Kurihara, B. J. Watkins, T. T. Tsuda, and T. Takahashi

J. Geophys. Res. Vol. 117 ( A05308 ) 2012.3

Generation of atmospheric gravity waves in the polar thermosphere in response to auroral activity Reviewed

Oyama, S., and B. J. Watkins

Space Science Review 2011.10

Fine structure of sporadic sodium layer observed with a sodium lidar at Tromsoe, Norway Reviewed Open Access

Tsuda, T. T., S. Nozawa, T. Kawahara, T. Kawabata, N. Saito, S. Wada, C. Hall, S. Oyama, Y. Ogawa, S. Suzuki, T. Ogawa, T. Takahashi, H. Fujiwara, R. Fujii, N. Matuura, and A. Brekke

Geophys. Res. Lett. 2011.9

Variance of the vertical ion speed measured with the EISCAT UHF radar in the polar lower ionosphere at Tromsoe, Norway Reviewed Open Access

Oyama, S., A. Brekke, T. T. Tsuda, J. Kurihara, and B. J. Watkins

J. Geophys. Res. Vol. 116 ( A00K06 ) 2011.7

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

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

Ann. Geophysicae Vol. 28 page： 1847-1857 2010.10

Language：English Publishing type：Research paper (scientific journal)

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

Open Access

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Papers - OYAMA, Shin-ichiro