研究者詳細 - 岩井　一正

論文 - 岩井　一正

分割表示 43 件中 1 - 20 件目／全件表示 >>

Automatic Detection of Type II Solar Radio Burst by Using 1-D Convolution Neutral Network 査読有り

56 巻 ( 2 ) 頁： 213 - 224 2023年12月

East–West Asymmetry in Interplanetary-Scintillation-Level Variation Associated with Solar-Wind Disturbances 査読有り

298 巻 ( 11 ) 2023年11月

Forecasting Heliospheric CME Solar-Wind Parameters Using the UCSD Time-Dependent Tomography and ISEE Interplanetary Scintillation Data: The 10 March 2022 CME 査読有り

Bernard V. Jackson, Munetoshi Tokumaru, Kazumasa Iwai, Matthew T. Bracamontes, Andrew Buffington, Ken’ichi Fujiki, Go Murakami, Daniel Heyner, Beatriz Sanchez-Cano, Mathias Rojo, Sae Aizawa, Nicolas Andre, Alain Barthe, Emmanuel Penou, Andrei Fedorov, Jean-Andre Sauvaud, Shoichiro Yokota, Yoshifumi Saito

Solar Physics 298 巻 ( 5 ) 2023年5月

掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media LLC

Abstract

Remotely sensed interplanetary scintillation (IPS) data from the Institute for Space-Earth Environmental Research (ISEE), Japan, allows a determination of solar-wind parameters throughout the inner heliosphere. We show the 3D analysis technique developed for these data sets that forecast plasma velocity, density, and component magnetic fields at Earth, as well at the other inner heliospheric planets and spacecraft. One excellent coronal mass ejection (CME) example that occurred on the 10 March 2022 was viewed not only in the ISEE IPS analyses, but also by the spacecraft near Earth that measured the CME arrival at one AU. Solar Orbiter, that was nearly aligned along the Earth radial at 0.45 AU, also measured the CME in plasma density, velocity, and magnetic field. BepiColombo at 0.42 AU was also aligned with the STEREO A spacecraft, and viewed this CME. The instruments used here from BepiColombo include: 1) the European-Space-Agency Mercury-Planetary-Orbiter magnetic field measurements; 2) the Japan Aerospace Exploration Agency Mio spacecraft Solar Particle Monitor that viewed the CME Forbush decrease, and the Mercury Plasma Experiment/Mercury Electron Analyzer instruments that measured particles and solar-wind density from below the spacecraft protective sunshield covering. This article summarizes the analysis using ISEE, Japan real-time data for these forecasts: it provides a synopsis of the results and confirmation of the CME event morphology after its arrival, and discusses how future IPS analyses can augment these results.

DOI： 10.1007/s11207-023-02169-8

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その他リンク： https://link.springer.com/article/10.1007/s11207-023-02169-8/fulltext.html

Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24 査読有り

Munetoshi Tokumaru, Ken'ichi Fujiki, Kazumasa Iwai

SOLAR PHYSICS 298 巻 ( 2 ) 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Interplanetary scintillation (IPS) analysis is an effective technique for remotely sensing solar-wind disturbances, such as stream-interaction regions (SIRs) and coronal mass ejections (CMEs), which are the main drivers of space weather. Here, we employed 327-MHz IPS observations conducted at the Institute of Space-Earth Environmental Research, Nagoya University for the period of 1997 - 2019 to determine IPS indices that represent the density-fluctuation level of the inner heliosphere. We then compared these indices with the solar-wind density and speed measured near the Earth. Consequently, we found weak but significant positive correlations between the IPS indices and both the solar-wind density and speed gradient at a time lag of 0 days. This suggests that an increase in IPS indices corresponds to the arrival of the compression region associated with SIR or CME at the Earth, which is consistent with model calculations. Significant negative correlations were observed between the IPS and disturbance storm time (Dst) indices at a time lag of a few days; however, the correlations were too weak to enable reliable predictions of space weather. Possible reasons for these weak correlations are also discussed. Using the IPS indices, we determined the solar-cycle variation in the occurrence rate of solar-wind disturbances for the analysis period. The occurrence rates exhibited two maxima corresponding to the solar maximum and minimum, which are generally consistent with the combined effects of CME and SIR. The lower occurrence rates in Cycle 24 than in Cycle 23 reflect a weaker solar activity. These results suggest that the proposed IPS indices are useful for studying the long-term characteristics of solar-wind disturbances.

DOI： 10.1007/s11207-023-02116-7

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Solar observing with the Atacama large millimeter-submillimeter array 査読有り

T. S. Bastian, M. Shimojo, M. Bárta, S. M. White, K. Iwai

Frontiers in Astronomy and Space Sciences 9 巻 2022年10月

掲載種別：研究論文（学術雑誌）出版者・発行元：Frontiers Media SA

The Atacama Large Millimeter-submillimeter Array (ALMA), sited on the high desert plains of Chajnantor in Chile, has opened a new window onto solar physics in 2016 by providing continuum observations at millimeter and sub-millimeter wavelengths with an angular resolution comparable to that available at optical (O), ultraviolet (UV), extreme ultraviolet (EUV), and X-ray wavelengths, and with superior time resolution. In the intervening years, progress has been made testing and commissioning new observing modes and capabilities, in developing data calibration strategies, and in data imaging and restoration techniques. Here we review ALMA current solar observing capabilities, the process by which a user may propose to use the instrument, and summarize the observing process and work flow. We then discuss some of the challenges users may encounter in imaging and analyzing their data. We conclude with a discussion of additional solar observing capabilities and modes under consideration that are intended to further exploit the unique spectral coverage provided by ALMA.

DOI： 10.3389/fspas.2022.977368

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Magnetohydrodynamic simulation of coronal mass ejections using interplanetary scintillation data observed from radio sites ISEE and LOFAR 査読有り

Kazumasa Iwai, Richard A. Fallows, Mario M. Bisi, Daikou Shiota, Bernard V. Jackson, Munetoshi Tokumaru, Ken'ichi Fujiki

Advances in Space Research 2022年9月

Application of novel interplanetary scintillation visualisations using LOFAR: A case study of merged CMEs from September 2017 査読有り

R.A. Fallows, K. Iwai, B.V. Jackson, P. Zhang, M.M. Bisi, P. Zucca

Advances in Space Research 2022年9月

Over seven decades of solar microwave data obtained with Toyokawa and Nobeyama Radio Polarimeters 査読有り

Masumi Shimojo, Kazumasa Iwai

Geoscience Data Journal 2022年6月

Testing the Alfvén-wave Model of the Solar Wind with Interplanetary Scintillation 査読有り

Munehito Shoda, Kazumasa Iwai, Daikou Shiota

The Astrophysical Journal 928 巻 ( 2 ) 頁： 130 - 130 2022年4月

掲載種別：研究論文（学術雑誌）出版者・発行元：American Astronomical Society

Abstract

Understanding the mechanism(s) of solar wind acceleration is important in astrophysics and geophysics. A promising model of solar wind acceleration is known as the wave/turbulence-driven (WTD) model, in which Alfvén waves feed energy to the solar wind. In this study, we tested the WTD model with global measurements of wind speed from interplanetary scintillation (IPS) observations. For Carrington rotations in minimal and maximal activity phases, we selected field lines calculated by the potential-field source-surface method in high and midlatitudes and compared the simulated and observed wind velocities. The simulation was performed in a self-consistent manner by solving the magnetohydrodynamic equations from the photosphere to the solar wind. In high-latitude regions, the simulated solar wind velocity agrees better with the IPS observation than with the classical Wang–Sheeley empirical estimation, both in maximal and minimal activity phases. In midlatitude regions, the agreement worsens, possibly because of the inaccuracy of the WTD model and/or the magnetic-field extrapolation. Our results indicate that the high-latitude solar wind is likely to be driven by waves and turbulence and that the physics-based prediction of the solar wind velocity is highly feasible with an improved magnetic-field extrapolation.

DOI： 10.3847/1538-4357/ac581e

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/ac581e/pdf

Global Distribution of the Solar Wind Speed Reconstructed from Improved Tomographic Analysis of Interplanetary Scintillation Observations between 1985 and 2019 査読有り

Munetoshi Tokumaru, Ken'ichi Fujiki, Masayoshi Kojima, Kazumasa Iwai

ASTROPHYSICAL JOURNAL 922 巻 ( 1 ) 2021年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing Ltd

Computer-assisted tomography (CAT) for interplanetary scintillation (IPS) observations enables the determination of the global distribution of solar wind speed. We compared solar wind speeds derived from the CAT analysis of IPS observations between 1985 and 2019 with in situ observations conducted by the near-Earth and Ulysses spacecraft. From this comparison, we found that solar wind speeds from the IPS observations for 2009-2019 were systematically higher than the in situ observations, whereas those for the period until 2008 were in good agreement with the in situ observations. Further, we found that the discrepancy between IPS and the in situ observations is improved by changing the power index of the empirical relation between the solar wind speed and density fluctuations. The CAT analysis using an optimal value for the power index determined from the comparison between IPS and in situ observations revealed long-term variations in the solar wind speed distribution over three cycles, leading to a better understanding of the time-varying global heliosphere. We found that polar solar winds become highly anisotropic at the Cycle 24/25 minimum, which is a peculiar aspect of this minimum. The IPS observations showed general agreement with the Parker Solar Probe observations around the perihelion of Orbit 1; this supports the reliability of the CAT analysis. The results of this study suggest that the physical properties of solar wind microturbulence may vary with a long-term decline in the solar activity, which provides important implication on the solar wind acceleration.

DOI： 10.3847/1538-4357/ac1862

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BepiColombo’s Cruise Phase: Unique Opportunity for Synergistic Observations 査読有り

L. Z. Hadid, V. Génot, S. Aizawa, A. Milillo, J. Zender, G. Murakami, J. Benkhoff, I. Zouganelis, T. Alberti, N. André, Z. Bebesi, F. Califano, A. P. Dimmock, M. Dosa, C. P. Escoubet, L. Griton, G. C. Ho, T. S. Horbury, K. Iwai, M. Janvier, E. Kilpua, B. Lavraud, A. Madar, Y. Miyoshi, D. Müller, R. F. Pinto, A. P. Rouillard, J. M. Raines, N. Raouafi, F. Sahraoui, B. Sánchez-Cano, D. Shiota, R. Vainio, A. Walsh

Frontiers in Astronomy and Space Sciences 8 巻 2021年9月

掲載種別：研究論文（学術雑誌）出版者・発行元：Frontiers Media SA

The investigation of multi-spacecraft coordinated observations during the cruise phase of BepiColombo (ESA/JAXA) are reported, with a particular emphasis on the recently launched missions, Solar Orbiter (ESA/NASA) and Parker Solar Probe (NASA). Despite some payload constraints, many instruments onboard BepiColombo are operating during its cruise phase simultaneously covering a wide range of heliocentric distances (0.28 AU–0.5 AU). Hence, the various spacecraft configurations and the combined in-situ and remote sensing measurements from the different spacecraft, offer unique opportunities for BepiColombo to be part of these unprecedented multipoint synergistic observations and for potential scientific studies in the inner heliosphere, even before its orbit insertion around Mercury in December 2025. The main goal of this report is to present the coordinated observation opportunities during the cruise phase of BepiColombo (excluding the planetary flybys). We summarize the identified science topics, the operational instruments, the method we have used to identify the windows of opportunity and discuss the planning of joint observations in the future.

DOI： 10.3389/fspas.2021.718024

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Venus's induced magnetosphere during active solar wind conditions at BepiColombo's Venus 1 flyby 査読有り

Martin Volwerk, Beatriz Sanchez-Cano, Daniel Heyner, Sae Aizawa, Nicolas Andre, Ali Varsani, Johannes Mieth, Stefano Orsini, Wolfgang Baumjohann, David Fischer, Yoshifumi Futaana, Richard Harrison, Harald Jeszenszky, Iwai Kazumasa, Gunter Laky, Herbert Lichtenegger, Anna Milillo, Yoshizumi Miyoshi, Rumi Nakamura, Ferdinand Plaschke, Ingo Richter, Sebastian Rojas Mata, Yoshifumi Saito, Daniel Schmid, Daikou Shiota, Cyril Simon Wedlund

ANNALES GEOPHYSICAE 39 巻 ( 5 ) 頁： 811 - 831 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：COPERNICUS GESELLSCHAFT MBH

Out of the two Venus flybys that BepiColombo uses as a gravity assist manoeuvre to finally arrive at Mercury, the first took place on 15 October 2020. After passing the bow shock, the spacecraft travelled along the induced magnetotail, crossing it mainly in the Yvso direction. In this paper, the BepiColombo Mercury Planetary Orbiter Magnetometer (MPO-MAG) data are discussed, with support from three other plasma instruments: the Planetary Ion Camera (SERENA-PICAM) of the SERENA suite, the Mercury Electron Analyser (MEA), and the BepiColombo Radiation Monitor (BERM). Behind the bow shock crossing, the magnetic field showed a draping pattern consistent with field lines connected to the interplanetary magnetic field wrapping around the planet. This flyby showed a highly active magnetotail, with e.g. strong flapping motions at a period of similar to 7 min This activity was driven by solar wind conditions. Just before this flyby, Venus's induced magnetosphere was impacted by a stealth coronal mass ejection, of which the trailing side was still interacting with it during the flyby. This flyby is a unique opportunity to study the full length and structure of the induced magnetotail of Venus, indicating that the tail was most likely still present at about 48 Venus radii.

DOI： 10.5194/angeo-39-811-2021

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PSTEP: project for solar-terrestrial environment prediction 査読有り

Kanya Kusano, Kiyoshi Ichimoto, Mamoru Ishii, Yoshizumi Miyoshi, Shigeo Yoden, Hideharu Akiyoshi, Ayumi Asai, Yusuke Ebihara, Hitoshi Fujiwara, Tada-Nori Goto, Yoichiro Hanaoka, Hisashi Hayakawa, Keisuke Hosokawa, Hideyuki Hotta, Kornyanat Hozumi, Shinsuke Imada, Kazumasa Iwai, Toshihiko Iyemori, Hidekatsu Jin, Ryuho Kataoka, Yuto Katoh, Takashi Kikuchi, Yuki Kubo, Satoshi Kurita, Haruhisa Matsumoto, Takefumi Mitani, Hiroko Miyahara, Yasunobu Miyoshi, Tsutomu Nagatsuma, Aoi Nakamizo, Satoko Nakamura, Hiroyuki Nakata, Naoto Nishizuka, Yuichi Otsuka, Shinji Saito, Susumu Saito, Takashi Sakurai, Tatsuhiko Sato, Toshifumi Shimizu, Hiroyuki Shinagawa, Kazuo Shiokawa, Daikou Shiota, Takeshi Takashima, Chihiro Tao, Shin Toriumi, Satoru Ueno, Kyoko Watanabe, Shinichi Watari, Seiji Yashiro, Kohei Yoshida, Akimasa Yoshikawa

EARTH PLANETS AND SPACE 73 巻 ( 1 ) 2021年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Although solar activity may significantly impact the global environment and socioeconomic systems, the mechanisms for solar eruptions and the subsequent processes have not yet been fully understood. Thus, modern society supported by advanced information systems is at risk from severe space weather disturbances. Project for solar-terrestrial environment prediction (PSTEP) was launched to improve this situation through synergy between basic science research and operational forecast. The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. By this project, we sought to answer the fundamental questions concerning the solar-terrestrial environment and aimed to build a next-generation space weather forecast system to prepare for severe space weather disasters. The PSTEP consists of four research groups and proposal-based research units. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

DOI： 10.1186/s40623-021-01486-1

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BepiColombo Science Investigations During Cruise and Flybys at the Earth, Venus and Mercury 査読有り

Mangano Valeria, Dosa Melinda, Franz Markus, Milillo Anna, Oliveira Joana S., Lee Yeon Joo, McKenna-Lawlor Susan, Grassi Davide, Heyner Daniel, Kozyrev Alexander S., Peron Roberto, Helbert Joern, Besse Sebastien, de la Fuente Sara, Montagnon Elsa, Zender Joe, Volwerk Martin, Chaufray Jean-Yves, Slavin James A., Krueger Harald, Maturilli Alessandro, Cornet Thomas, Iwai Kazumasa, Miyoshi Yoshizumi, Lucente Marco, Massetti Stefano, Schmidt Carl A., Dong Chuanfei, Quarati Francesco, Hirai Takayuki, Varsani Ali, Belyaev Denis, Zhong Jun, Kilpua Emilia K. J., Jackson Bernard V., Odstrcil Dusan, Plaschke Ferdinand, Vainio Rami, Jarvinen Riku, Ivanovski Stavro Lambrov, Madar Akos, Erdos Geza, Plainaki Christina, Alberti Tommaso, Aizawa Sae, Benkhoff Johannes, Murakami Go, Quemerais Eric, Hiesinger Harald, Mitrofanov Igor G., Iess Luciano, Santoli Francesco, Orsini Stefano, Lichtenegger Herbert, Laky Gunther, Barabash Stas, Moissl Richard, Huovelin Juhani, Kasaba Yasumasa, Saito Yoshifumi, Kobayashi Masanori, Baumjohann Wolfgang

SPACE SCIENCE REVIEWS 217 巻 ( 1 ) 2021年2月

Validation of coronal mass ejection arrival-time forecasts by magnetohydrodynamic simulations based on interplanetary scintillation observations 査読有り

Iwai Kazumasa, Shiota Daikou, Tokumaru Munetoshi, Fujiki Ken'ichi, Den Mitsue, Kubo Yuki

EARTH PLANETS AND SPACE 73 巻 ( 1 ) 2021年1月

Estimating the Temperature and Density of a Spicule from 100 GHz Data Obtained with ALMA 査読有り

Shimojo Masumi, Kawate Tomoko, Okamoto Takenori J., Yokoyama Takaaki, Narukagel Noriyuki, Sakao Taro, Iwai Kazumasa, Fleishman Gregory D., Shibatas Gazunari

ASTROPHYSICAL JOURNAL LETTERS 888 巻 ( 2 ) 2020年1月

Spectral Structures of Type II Solar Radio Bursts and Solar Energetic Particles 査読有り国際共著国際誌

Iwai Kazumasa, Yashiro Seiji, Nitta Nariaki V, Kubo Yuki

ASTROPHYSICAL JOURNAL 888 巻 ( 1 ) 2020年1月

Coordinated Interplanetary Scintillation Observations in Japan and Russia for Coronal Mass Ejection Events in Early September 2017 査読有り

Tokumaru Munetoshi, Fujiki Ken'ichi, Iwai Kazumasa, Tyul'bashev Sergey, Chashei Igor

SOLAR PHYSICS 294 巻 ( 7 ) 2019年7月

Development of a coronal mass ejection arrival time forecasting system using interplanetary scintillation observations 査読有り

Iwai Kazumasa, Shiota Daikou, Tokumaru Munetoshi, Fujiki Ken'ichi, Den Mitsue, Kubo Yuki

EARTH PLANETS AND SPACE 71 巻 2019年4月

Comparative Study of Microwave Polar Brightening, Coronal Holes, and Solar Wind over the Solar Poles 査読有り

Fujiki Ken'ichi, Shibasaki Kiyoto, Yashiro Seiji, Tokumaru Munetoshi, Iwai Kazumasa, Masuda Satoshi

SOLAR PHYSICS 294 巻 ( 3 ) 2019年3月

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