研究者業績

長谷川 洋

ハセガワ ヒロシ  (Hiroshi Hasegawa)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 助教

J-GLOBAL ID
200901040603353226
Researcher ID
A-1192-2007
researchmap会員ID
6000000662

外部リンク

論文

 160
  • H. Hasegawa, M. R. Argall, N. Aunai, R. Bandyopadhyay, N. Bessho, I. J. Cohen, R. E. Denton, J. C. Dorelli, J. Egedal, S. A. Fuselier, P. Garnier, V. Génot, D. B. Graham, K. J. Hwang, Y. V. Khotyaintsev, D. B. Korovinskiy, B. Lavraud, Q. Lenouvel, T. C. Li, Y.-H. Liu, B. Michotte de Welle, T. K. M. Nakamura, D. S. Payne, S. M. Petrinec, Y. Qi, A. C. Rager, P. H. Reiff, J. M. Schroeder, J. R. Shuster, M. I. Sitnov, G. K. Stephens, M. Swisdak, A. M. Tian, R. B. Torbert, K. J. Trattner, S. Zenitani
    Space Science Reviews 220(6) 2024年9月2日  査読有り筆頭著者責任著者
    Abstract There is ample evidence for magnetic reconnection in the solar system, but it is a nontrivial task to visualize, to determine the proper approaches and frames to study, and in turn to elucidate the physical processes at work in reconnection regions from in-situ measurements of plasma particles and electromagnetic fields. Here an overview is given of a variety of single- and multi-spacecraft data analysis techniques that are key to revealing the context of in-situ observations of magnetic reconnection in space and for detecting and analyzing the diffusion regions where ions and/or electrons are demagnetized. We focus on recent advances in the era of the Magnetospheric Multiscale mission, which has made electron-scale, multi-point measurements of magnetic reconnection in and around Earth’s magnetosphere.
  • Abraham Chian, Rodrigo Miranda, Cesar Bertucci, Xóchitl Blanco-Cano, Joe Borovsky, Sergio Dasso, Ezequiel Echer, Adriane Franco, Kirolosse M. Girgis, J. Americo Gonzalez-Esparza, Tohru Hada, Hiroshi Hasegawa, Syau-Yun Hsieh, Primoz Kajdič, Christian Mazelle, Erico Rempel, Diana Rojas-Castillo, Beatriz Sanchez-Cano, David Sibeck, Marina Stepanova, José Valdés-Galicia, Juan Valdivia
    Journal of Atmospheric and Solar-Terrestrial Physics 106253-106253 2024年5月  査読有り
  • Shuo Wang, Ying Zou, Qiang Hu, Xueling Shi, Hiroshi Hasegawa
    Journal of Geophysical Research: Space Physics 129(2) 2024年2月7日  査読有り
    Abstract Flux transfer events (FTEs) are a type of magnetospheric phenomena that exhibit distinctive observational signatures from the in situ spacecraft measurements. They are generally believed to possess a magnetic field configuration of a magnetic flux rope and formed through magnetic reconnection at the dayside magnetopause, sometimes accompanied with enhanced plasma convection in the ionosphere. We examine two FTE intervals under the condition of southward interplanetary magnetic field (IMF) with a dawn‐dusk component. We apply the Grad‐Shafranov (GS) reconstruction method to the in situ measurements by the Magnetospheric Multiscale (MMS) spacecraft to derive the magnetic flux contents associated with the FTE flux ropes. In particular, given a cylindrical magnetic flux rope configuration derived from the GS reconstruction, the magnetic flux content can be characterized by both the toroidal (axial) and poloidal fluxes. We then estimate the amount of magnetic flux (i.e., the reconnection flux) encompassed by the area “opened” in the ionosphere, based on the ground‐based Super Dual Auroral Radar Network (SuperDARN) observations. We find that for event 1, the FTE flux rope is oriented in the approximate dawn‐dusk direction, and the amount of its total poloidal magnetic flux falls within the range of the corresponding reconnection flux. For event 2, the FTE flux rope is oriented in the north‐south direction. Both the FTE flux and the reconnection flux have greater uncertainty. We provide a detailed description about a formation scenario of sequential magnetic reconnection between adjacent field lines based on the FTE flux rope configurations from our results.
  • Richard E. Denton, Yi‐Hsin Liu, Jefferson A. Agudelo Rueda, Kevin J. Genestreti, Hiroshi Hasegawa, Martin Hosner, Roy B. Torbert, James L. Burch
    Journal of Geophysical Research: Space Physics 129(1) 2024年1月17日  査読有り
    Abstract An LMN coordinate system for magnetic reconnection events is sometimes determined by defining N as the direction of the gradient across the current sheet and L as the direction of maximum variance of the magnetic field. The third direction, M, is often assumed to be the direction of zero gradient, and thus the orientation of the X line. But when there is a guide field, the X line direction may have a significant component in the L direction defined in this way. For a 2D description, a coordinate system describing such an event would preferably be defined using a different coordinate direction M′ oriented along the X line. Here we use a 3D particle‐in‐cell simulation to show that the X line is oriented approximately along the direction bisecting the asymptotic magnetic field directions on the two sides of the current sheet. We describe two possible ways to determine the orientation of the X line from spacecraft data, one using the minimum gradient direction from Minimum Directional Derivative analysis at distances of the order of the current sheet thickness from the X line, and another using the bisection direction based on the asymptotic magnetic fields outside the current sheet. We discuss conditions for validity of these estimates, and we illustrate these conditions using several Magnetospheric Multiscale (MMS) events. We also show that intersection of a flux rope due to secondary reconnection with the primary X line can destroy invariance along the X line and negate the validity of a two‐dimensional description.
  • K.-J. Hwang, R. Nakamura, J. P. Eastwood, S. A. Fuselier, H. Hasegawa, T. Nakamura, B. Lavraud, K. Dokgo, D. L. Turner, R. E. Ergun, P. H. Reiff
    Space Science Reviews 219(8) 2023年10月30日  査読有り
    Abstract Various physical processes in association with magnetic reconnection occur over multiple scales from the microscopic to macroscopic scale lengths. This paper reviews multi-scale and cross-scale aspects of magnetic reconnection revealed in the near-Earth space beyond the general global-scale features and magnetospheric circulation organized by the Dungey Cycle. Significant and novel advancements recently reported, in particular, since the launch of the Magnetospheric Multi-scale mission (MMS), are highlighted being categorized into different locations with different magnetic topologies. These potentially paradigm-shifting findings include shock and foreshock transient driven reconnection, magnetosheath turbulent reconnection, flow shear driven reconnection, multiple X-line structures generated in the dayside/flankside/nightside magnetospheric current sheets, development and evolution of reconnection-driven structures such as flux transfer events, flux ropes, and dipolarization fronts, and their interactions with ambient plasmas. The paper emphasizes key aspects of kinetic processes leading to multi-scale structures and bringing large-scale impacts of magnetic reconnection as discovered in the geospace environment. These key features can be relevant and applicable to understanding other heliospheric and astrophysical systems.

MISC

 25

書籍等出版物

 2

講演・口頭発表等

 127

所属学協会

 1

共同研究・競争的資金等の研究課題

 7