News Item
Multidisciplinary Sciences
Elizabeth Gibney
Summary: This mission aims to enhance forecasts of damaging space weather.
News Item
Multidisciplinary Sciences
Alexandra Witze
Summary: The emails reveal the controversial response of the agency to astronomers' concerns about past LGBT+ discrimination.
News Item
Multidisciplinary Sciences
Alexandra Witze
Summary: Some astronomers argue that the flagship observatory will memorialize discrimination, while others are waiting for more evidence.
Article
Astronomy & Astrophysics
Zdenek Hrazdira, Miloslav Druckmueller, Shadia Habbal
Summary: A novel iterative phase correlation technique is proposed for reliable inference of the differential rotation rate of the solar photosphere, without the need for specific reference features or extended observations.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2021)
Article
Astronomy & Astrophysics
G. Mann, A. Warmuth, H. Oenel
Summary: By observing seven class 1 extreme-ultraviolet (EUV) waves in the solar corona, researchers find a relationship between initial velocity and deceleration, which agrees with the theory of large-amplitude magnetohydrodynamic (MHD) waves.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Bin Zhuang, Noe Lugaz, Tingyu Gou, Liuguan Ding
Summary: The study revealed that in the scenario of twin coronal mass ejections (CMEs), the speed of the primary CME (priCME) has the highest correlation with the peak intensity of solar energetic particles (SEPs). Furthermore, the combination of CME speed and propagation direction showed a higher correlation with SEP peak intensity. This indicates the dominant role of priCME in controlling SEP enhancements and emphasizes the consideration of latitudinal effects.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Gottfried Mann, Astrid M. Veronig
Summary: This article investigates a dome-shaped extreme-ultraviolet (EUV) wave observed by the EUVI instrument on the STEREO-B spacecraft, which reveals the three-dimensional propagation characteristics of a large-scale EUV wave in the solar corona, considered to be a manifestation of a large-amplitude magnetohydrodynamic (MHD) wave. By measuring the velocity of the EUV wave across the solar surface, the magnetic field of the quiet Sun is determined to be approximately 3.2 G. This study shows that the propagation of the dome-shaped EUV wave can be well described by the theory of large amplitude (simple) MHD waves.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Aiying Duan, Chaowei Jiang, ZhenJun Zhou, Xueshang Feng
Summary: This paper investigates the initiation mechanism of the first on-disk X-class eruptive flare in solar cycle 25. The study reveals a magnetic flux rope (MFR) consistent with a pre-existing filament before the flare, suggesting that the eruption of the whole filament indicates the eruption of the MFR. Quantitative analysis shows that the pre-flare MFR resides too low to trigger a torus instability, while the pre-flare evolution of the current density suggests the formation of a vertical current sheet before the eruption. The study suggests that the event follows a reconnection-based initiation mechanism, in which the eruption is initiated by reconnection in a gradually formed current sheet.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
S. N. A. Syed Zafar, R. Umar, N. H. Sabri, M. H. Jusoh, A. N. Dagang, A. Yoshikawa
Summary: Previous studies have shown that solar activities such as coronal mass ejections and solar flares can lead to the development of storms and high-speed streams. This study investigates the response of the geomagnetic index SYM/H to solar wind parameters, as well as the ground geomagnetic field responses at low-latitude stations. Findings suggest delayed response of the Earth's magnetosphere to weak geomagnetic storms, while strong solar wind and IMF variations can excite the Earth's H-component during geomagnetic storms caused by solar activities.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
R. Bucik, G. M. Mason, R. Gomez-Herrero, V Krupar, D. Lario, M. J. Starkey, G. C. Ho, J. Rodriguez-Pacheco, R. F. Wimmer-Schweingruber, F. Espinosa Lara, T. Tadesse, L. Balmaceda, C. M. S. Cohen, M. A. Dayeh, M. Desai, P. Kuehl, N. Nitta, M. E. Wiedenbeck, Z. G. Xu
Summary: The origin of He-3 abundance enhancements in gradual solar energetic particle (SEP) events remains largely unexplained. Two possible mechanisms have been suggested: the reacceleration of remnant flare material by coronal mass ejection (CME)-driven shocks in interplanetary space, and concomitant activity in the corona. Analysis of the first gradual SEP event with enhanced He-3 abundance observed by Solar Orbiter suggests that the most probable cause of the enhancement is residual He-3 ions remaining from a preceding long period of He-3-rich SEPs.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Sumanth Rotti, Berkay Aydin, Manolis K. Georgoulis, Petrus C. Martens
Summary: We present a catalog of solar energetic particle (SEP) events covering solar cycles 22, 23 and 24 and integrate three existing catalogs based on satellite data. The catalog includes 341 SEP events, of which 245 events reach the threshold for significant proton events. Researchers can access time-series data and intensity profiles of proton fluxes for each event, aiding understanding of SEPs and their source eruption characteristics for space weather prediction.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2022)
Article
Astronomy & Astrophysics
L. Makrygianni, J. Mullaney, V. Dhillon, S. Littlefair, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, R. Cutter, Y. -L. Mong, D. Steeghs, D. K. Galloway, P. O'Brien, G. Ramsay, S. Poshyachinda, R. Kotak, L. Nuttall, E. Palle, D. Pollacco, E. Thrane, S. Aukkaravittayapun, S. Awiphan, R. P. Breton, U. Burhanudin, P. Chote, A. Chrimes, E. Daw, C. Duffy, R. Eyles-Ferris, B. Gompertz, T. Heikkila, P. Irawati, M. Kennedy, T. Killestein, A. Levan, T. Marsh, D. Mata-Sanchez, S. Mattila, J. Maund, J. McCormac, D. Mkrtichian, E. Rol, U. Sawangwit, E. Stanway, R. Starling, P. A. Strom, S. Tooke, K. Wiersema
Summary: The study adapted LSST Science Pipelines to process data from the GOTO prototype, achieving a photometry precision better than 20 mmag for sources brighter than 16 mag. Comparisons with other photometry measurements showed good agreement and repeatability, demonstrating the robustness of the LSST Software Pipelines in delivering accurate forced photometry measurements from GOTO data.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF AUSTRALIA
(2021)
Article
Astronomy & Astrophysics
Robert F. Wimmer-Schweingruber, Lars Berger, Alexander Kollhoff, Patrick Kuehl, Bernd Heber, Liu Yang, Verena Heidrich-Meisner, Andreas Klassen, Raul Gomez-Herrero, Javier Rodriguez-Pacheco, George C. Ho, Glenn M. Mason, Nils P. Janitzek, Athanasios Kouloumvakos, Linghua Wang, Alexander Warmuth, David Lario, Fernando Carcaboso, Christopher J. Owen, Radoslav Buik, Daniel Pacheco, Olga Malandraki, Robert C. Allen, Luciano Rodriguez, Daria Shukhobodskaia, Francisco Espinosa Lara, Ignacio Cernuda, Stephan I. Boettcher, Sandra Eldrum, Sebastian Fleth, Zigong Xu
Summary: This study observed an unusual solar particle event where the path length of electrons and ions was three times longer than the standard spiral length, yet they still followed the same magnetic field structures. This event offers important opportunities to study the transport of SEPs within interplanetary structures.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
D. E. Morosan, J. Pomoell, A. Kumari, E. K. J. Kilpua, R. Vainio
Summary: The Sun produces powerful solar flares and coronal mass ejections (CMEs) which can accelerate electron beams and generate radio bursts. This study investigates the physical mechanism responsible for a type II burst that occurs in the absence of a CME.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Susan W. Samwel, Rositsa Miteva
Summary: This study presents a comprehensive catalogue of solar energetic electron events observed during solar cycles 23 and 24 in the energy range of 103-315 keV. The analysis includes the correlation between electron enhancements and solar activities such as solar flares and coronal mass ejections, as well as their correlation with solar energetic protons. The catalogue aims to provide a publicly available service and is considered a novel tool for real-time particle forecasting systems to mitigate harmful space weather effects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Hisashi Hayakawa, Denny M. Oliveira, Margaret A. Shea, Don F. Smart, Sean P. Blake, Kentaro Hattori, Ankush T. Bhaskar, Juan J. Curto, Daniel R. Franco, Yusuke Ebihara
Summary: In late March 1940, there were at least five significant solar flares that likely launched interplanetary coronal mass ejections (ICMEs) and caused one of the largest storm sudden commencements (SSCs) since 1868. These events had significant societal impacts and pose potential space weather hazards. The analysis of this historical event provides insights into possible serious space weather hazards and serves as a quantitative basis for future analyses and predictions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Yusuke Ebihara, Takashi Tanaka
Summary: This study investigates the generation regions of Region 1 field-aligned currents (FACs) using global magnetohydrodynamics (MHD) simulation. Unlike conventional methods, this study considers the Alfven traveling time and background motion of plasma. The results show that the flank magnetopause is a major generator region, where solar wind-originated plasma and magnetosphere-originated plasma participate in the generation of FACs.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Hisashi Hayakawa, Heikki Nevanlinna, Sean P. Blake, Yusuke Ebihara, Ankush T. Bhaskar, Yoshizumi Miyoshi
Summary: The Carrington storm in September 1859 is considered the most powerful geomagnetic storm ever recorded. This study reconstructed the geomagnetic disturbances during the Carrington storm based on data from the Colaba H magnetometer in India, and found discrepancies between hourly and spot measurements.
ASTROPHYSICAL JOURNAL
(2022)
Review
Geosciences, Multidisciplinary
Hisashi Hayakawa, Yusuke Ebihara, Hidetoshi Hata
Summary: Solar Cycle 19 was the greatest solar cycle in the last four centuries, causing multiple solar eruptions and geomagnetic storms. The International Geophysical Year captured extreme space weather events, including the third and fourth largest geomagnetic storms. This article reviews Japanese auroral observations during this period and provides references for future discussions on auroral activities during intense space weather events.
GEOSCIENCE DATA JOURNAL
(2023)
Article
Astronomy & Astrophysics
Takashi Kikuchi, Tohru Araki, Kumiko K. Hashimoto, Yusuke Ebihara, Takashi Tanaka, Yukitoshi Nishimura, Geeta Vichare, Ashwini K. Sinha, Jaroslav Chum, Keisuke Hosokawa, Ichiro Tomizawa, Yoshimasa Tanaka, Akira Kadokura
Summary: This article aims to provide a consistent understanding of the observation, theoretical model, and simulation of the geomagnetic sudden commencement (SC) observed on May 12, 2021. The study reveals various characteristics and relationships in different regions, and proposes an explanation based on the TM0/TEM mode wave.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2022)
Article
Astronomy & Astrophysics
T. Tanaka, Y. Ebihara, M. Watanabe, S. Fujita, N. Nishitani, R. Kataoka
Summary: The theta aurora phenomenon is reproduced through global simulation in this paper. The formation mechanism and magnetospheric topology of the theta aurora are explained in detail.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
T. Sakurai, A. N. Wright, K. Takahashi, T. Elsden, Y. Ebihara, N. Sato, A. Kadokura, Y. Tanaka, T. Hori
Summary: A one-to-one correspondence is found between poleward moving auroral arcs (PMAAs) and H-component of magnetic field Pc5 oscillations. PMAAs are most prominent at a magnetic latitude of 69 degrees and exhibit features of field-line resonances. Ground-based Pc5 oscillations are observed concurrently with toroidal mode Pc5 oscillations observed by THEMIS satellites. Numerical modeling shows that the magnetic energy of Pc5 oscillations is much larger than the kinetic energy, indicating the importance of magnetic energy in producing auroral emissions in the ionosphere.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Megha Pandya, Veenadhari Bhaskara, Yusuke Ebihara, G. D. Reeves
Summary: This study investigates the dynamics of ion fluxes during geomagnetic storms caused by two different categories of solar wind drivers using high-resolution data from the entire Van Allen Probes era. The study reveals differences in the response of ions with different energies and L-values to solar wind parameters and magnetic storm strength. Additionally, the duration and timing of O+, He+, and H+ ion appearance vary.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
T. Tanaka, M. Watanabe, Y. Ebihara, S. Fujita, N. Nishitani, R. Kataoka
Summary: This article investigates the relationship between field-aligned current (FAC) and arc aurora, and finds that the numerically reproduced FAC matches well with the observed arc aurora in terms of morphology. The study also reveals that the occurrence of arc aurora and FAC is closely controlled by convection structure.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Yusuke Ebihara, Takashi Tanaka
Summary: We investigated the generation processes of field-aligned currents (FACs) that intensify abruptly at the beginning of the substorm expansion phase. We traced the backward path of an Alfven wave in the global MHD simulation and found that the generation region is the near-Earth plasma sheet. The near-Earth FAC dynamo involves the movement of plasma, Ampere and Faraday laws, and the conversion of field-perpendicular current to FACs.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
T. Tanaka, Y. Ebihara, M. Watanabe, S. Fujita, R. Kataoka
Summary: The study investigates the interaction between the solar wind, Jovian magnetosphere, and ionosphere through global magnetohydrodynamic simulation. The simulation successfully reproduces various phenomena such as the confinement of Jovian magnetic field, distributions of ions, interchange instability, and current system that maintains co-rotation. The transport mechanism of Io plasma gradually changes from the Io torus to the distant tail, with different dominant factors at different distances. The study also reveals the connection between field-aligned current and ionospheric emissions.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Shotaro Sakai, Kanako Seki, Naoki Terada, Hiroyuki Shinagawa, Ryoya Sakata, Takashi Tanaka, Yusuke Ebihara
Summary: The rotation of the interplanetary magnetic field (IMF) provides details of the escape mechanism that varies with the interaction between the intrinsic magnetic field and the IMF. A multispecies magnetohydrodynamic simulation on a Mars-like planet reveals that the total ion escape rate increases significantly when the IMF rotates from due north to clock angles of 45 degrees-75 degrees, followed by a gentle increase until the IMF rotates to due south. The trigger for the large increase is multiple reconnections in the magnetospheric flank region, and the subsequent increase is due to the expansion of the reconnection area into the equatorial region. The IMF rotation could have implications for exoplanets orbiting in the vicinity of M-dwarfs.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Megha Pandya, Yusuke Ebihara, Takashi Tanaka, Jerry W. Manweiler
Summary: Zebra stripes refer to the repeated hills and valleys in the electron flux intensities below L = 3. By modeling advection with time-dependent electric fields, we investigate the properties and evolution of electron zebra stripes. The simulation shows that enhanced westward electric field transients cause inward motion of electrons, resulting in the formation of zebra stripes. The distribution of the westward electric field on the nightside is consistent with observations. Zebra stripes are a mixture of electrons that have and have not undergone inward transport via solar wind-inner magnetosphere coupling through the ionosphere.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Hisashi Hayakawa, Edward W. Cliver, Frederic Clette, Yusuke Ebihara, Shin Toriumi, Ilaria Ermolli, Theodosios Chatzistergos, Kentaro Hattori, Delores J. Knipp, Sean P. Blake, Gianna Cauzzi, Kevin Reardon, Philippe-A. Bourdin, Dorothea Just, Mikhail Vokhmyanin, Keitaro Matsumoto, Yoshizumi Miyoshi, Jose R. Ribeiro, Ana P. Correia, David M. Willis, Matthew N. Wild, Sam M. Silverman
Summary: This study reviews the extreme geomagnetic storm on February 4, 1872, analyzing its origins, characteristics, auroral visibility, and intensity compared to other extreme storms in 1859 and 1921. The 1872 storm is considered among the three largest magnetic storms observed, with strength and scale comparable to the extreme storms of 1859 and 1921.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
T. Zhang, Y. Ebihara, T. Tanaka
Summary: By performing a global magnetohydrodynamic simulation, magnetic disturbances on the ground at high-latitudes in response to jumps in solar wind dynamic pressure were investigated. The nighttime polar region is shown to be sensitive to hazardous geomagnetically induced currents caused by large-amplitude jumps in solar wind dynamic pressure.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2023)
