大学院工学研究院

大矢 浩代

オオヤ ヒロヨ  (Hiroyo Ohya)

基本情報

所属
千葉大学 大学院工学研究院基幹工学専攻電気電子工学コース 助教
学位
博士(理学)(名古屋大学)

研究者番号
00241943
J-GLOBAL ID
200901034091674769
researchmap会員ID
1000249464

論文

 20
  • Hiroyo Ohya, Fuminori Tsuchiya, Tamio Takamura, Hiroyuki Shinagawa, Yukihiro Takahashi, Alfred B. Chen
    Scientific Reports 14(1) 2024年7月16日  査読有り筆頭著者責任著者
    Abstract The submarine volcano Hunga Tonga–Hunga Ha’apai erupted explosively on January 15, 2022, offering a unique opportunity to investigate interactions between the atmosphere and ionosphere caused by Lamb and Pekeris waves. However, the resonance of Pekeris waves has not been previously detected. In this study, we applied a multi-point monitoring approach focusing on the lower ionosphere and atmospheric electric field. Here we show observed oscillations of 100–200 s in manmade transmitter signals and the magnetic and atmospheric electric fields, which were caused by Pekeris waves. However, no corresponding changes with the period of 100–200 s in atmospheric pressure due to Pekeris waves were observed on the ground. A simulation of neutral wind revealed Pekeris waves oscillating near the mesopause, suggesting resonance. Therefore, the oscillation in atmospheric electric field is interpreted that the resonance in the lower ionosphere was projected onto the Earth's surface via a global electric circuit.
  • Hisato Iwashita, Fumiaki Kobayashi, Kazuomi Morotomi, Shigeharu Shimamura, Atsushi Higuchi, Hiroyo Ohya, Toshiaki Takano, Tamio Takamura
    URSI Radio Science Letters 5 2024年4月  査読有り
  • H. Ohya, T. Suzuki, F. Tsuchiya, H. Nakata, K. Shiokawa
    Radio Science 59(3) 2024年2月26日  査読有り筆頭著者責任著者
    Abstract Several studies have examined ionospheric variation associated with meteorites, meteoroids, or meteors based on Global Satellite Navigation System total electron content observations. However, there have been few quantitative studies of the D‐region of the ionosphere (60–90 km), which is associated with meteoroids. We investigated variation in the D‐region during the passage of a meteoroid over northeastern Hokkaido, Japan, at 11:55:55 UT on 18 October 2018, using very low‐frequency (VLF, 3–30 kHz) and low‐frequency (LF, 30–300 kHz) signals observed by three transmitters [JJY (40 kHz), JJY (60 kHz), and JJI (22.2 kHz)], at Rikubetsu, Japan. Periodic variation of 100–200 s was observed in the VLF and LF amplitudes upon arrival of the acoustic wave. The vertical seismic velocity of Hi‐net and F‐net data also showed acoustic waves. Although the main period of the acoustic wave was 0.1–0.5 s in the seismic data, a longer period component (100–200 s) remained during propagation up to the D‐region ionosphere. The estimated velocity of the acoustic waves was ∼340 m/s on the ground according to the Hi‐net seismic data. The acoustic wave originated near the endpoint (25 km altitude) of the meteoroid trajectory. Based on the observed propagation time of the acoustic waves and ray tracing results, the acoustic waves propagated obliquely from near the endpoint of the meteoroid trajectory up to a D‐region height (about ∼90 km altitude), south of the Rikubetsu receiver.
  • T. Watanabe, M. Kobayashi, Y. Katoh, K. Shiokawa, H. Ohya, K. Suzuki, S. Tanaka, Y. Ishihara, T. Yamada, M. Yoshikawa
    WGN (Journal of the International Meteor Organization) 51(3) 2023年6月  
  • Jaroslav Chum, Tereza Šindelářová, Petra Koucká Knížová, Kateřina Podolská, Jan Rusz, Jiří Baše, Hiroyuki Nakata, Keisuke Hosokawa, Michael Danielides, Carsten Schmidt, Leon Knez, Jann-Yenq Liu, María Graciela Molina, Mariano Fagre, Zama Katamzi-Joseph, Hiroyo Ohya, Tatsuya Omori, Jan Laštovička, Dalia Obrazová Burešová, Daniel Kouba, Jaroslav Urbář, Vladimír Truhlík
    Geophysical Journal International 233(2) 1429-1443 2022年12月24日  査読有り
    Summary The massive explosive eruption of the Hunga volcano on 15 January 2022 generated atmospheric waves that were recorded around the globe and affected the ionosphere. The paper focuses on observations of atmospheric waves in the troposphere and ionosphere in Europe, however, a comparison with observations in East Asia, South Africa and South America is also provided. Unlike most recent studies of waves in the ionosphere based on the detection of changes in the total electron content, this study builds on detection of ionospheric motions at specific altitudes using continuous Doppler sounding. In addition, much attention is paid to long-period infrasound (periods longer than ∼50 s), which in Europe is observed simultaneously in the troposphere and ionosphere about an hour after the arrival of the first horizontally propagating pressure pulse (Lamb wave). It is shown that the long-period infrasound propagated approximately along the shorter great circle path, similar to the previously detected pressure pulse in the troposphere. It is suggested that the infrasound propagated in the ionosphere probably due to imperfect refraction in the lower thermosphere. The observation of infrasound in the ionosphere at such large distances from the source (over 16 000 km) is rare and differs from ionospheric infrasound detected at large distances from the epicenters of strong earthquakes, because in the latter case the infrasound is generated locally by seismic waves. An unusually large traveling ionospheric disturbance (TID) observed in Europe and associated with the pressure pulse from the Hunga eruption is also discussed. Doppler sounders in East Asia, South Africa and South America did not record such a significant TID. However, TIDs were observed in East Asia around times when Lamb waves passed the magnetically conjugate points. A probable observation of wave in the mesopause region in Europe approximately 25 min after the arrival of pressure pulse in the troposphere using a 23.4 kHz signal from a transmitter 557 km away and a coincident pulse in electric field data are also discussed.

MISC

 122

講演・口頭発表等

 20

担当経験のある科目(授業)

 6

共同研究・競争的資金等の研究課題

 7

社会貢献活動

 7