Review
Astronomy & Astrophysics
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
Summary: This paper reviews the multi-scale and cross-scale aspects of magnetic reconnection in the near-Earth space and emphasizes the key aspects of kinetic processes and the large-scale impacts of magnetic reconnection in the geospace environment. These findings have the potential to be relevant and applicable to understanding other heliospheric and astrophysical systems.
SPACE SCIENCE REVIEWS
(2023)
Article
Astronomy & Astrophysics
K-J. Hwang, K. Dokgo, E. Choi, J. L. Burch, D. G. Sibeck, B. L. Giles, C. Norgren, T. K. M. Nakamura, D. B. Graham, Y. Khotyaintsev, Q. Q. Shi, D. J. Gershman, C. J. Pollock, R. E. Ergun, R. B. Torbert, C. T. Russell, R. J. Strangeway
Summary: The study observed a bifurcated current sheet at the boundary of Kelvin-Helmholtz vortices (KHVs) and investigated the structure and formation mechanisms of current sheets. It identified three separate current sheets in different regions, highlighting the importance of electron anisotropy and diamagnetic currents in the presence of density asymmetry and weak velocity shear. The study also found that the combined effects of strong guide field, low density asymmetry, and weak flow shear contribute to the asymmetries in current-layer structure.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2021)
Article
Geosciences, Multidisciplinary
K. A. Blasl, T. K. M. Nakamura, R. Nakamura, A. Settino, H. Hasegawa, Z. Voros, M. Hosner, D. Schmid, M. Volwerk, Owen W. Roberts, E. Panov, Yi-Hsin Liu, F. Plaschke, J. E. Stawarz, J. C. Holmes
Summary: Magnetospheric Multiscale observations reveal an electron-scale reconnecting current sheet in the mixing region of a Kelvin-Helmholtz vortex. The intense electrostatic wave activity and consistent simulation results suggest a temporal evolution of the observed current sheet.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Astronomy & Astrophysics
Haomin Sun, Yan Yang, Quanming Lu, San Lu, Minping Wan, Rongsheng Wang
Summary: Using MHD simulations, this study investigates the physical regimes and the role of turbulence in turbulent reconnection. The results show that externally injected turbulence enhances the reconnection rate by converting magnetic energy to kinetic energy. The presence of turbulence also impacts the magnetic energy conversion and the Kelvin-Helmholtz instability in the reconnection process.
ASTROPHYSICAL JOURNAL
(2022)
Article
Geosciences, Multidisciplinary
K. A. Blasl, T. K. M. Nakamura, R. Nakamura, A. Settino, H. Hasegawa, Z. Voeroes, M. Hosner, D. Schmid, M. Volwerk, Owen W. Roberts, E. Panov, Yi-Hsin Liu, F. Plaschke, J. E. Stawarz, J. C. Holmes
Summary: This article presents observations of an electron-scale reconnecting current sheet in the mixing region along the trailing edge of a Kelvin-Helmholtz vortex. Consistencies between the observations and a realistic simulation indicate a temporal evolution of the observed electron-scale reconnection current sheet. The multi-scale and inter-process character of this event is important in understanding plasma mixing connected to the Kelvin-Helmholtz instability and the temporal evolution of electron-scale reconnection.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Physics, Fluids & Plasmas
M. Faganello, M. Sisti, F. Califano, B. Lavraud
Summary: A 3D two-fluid simulation shows the nonlinear development of the Kelvin-Helmholtz instability at the Earth's magnetopause, including the development of complex magnetic topology, vortex merging, and secondary instabilities. The study finds that there is a difference in the distribution of reconnection events between the Southern Hemisphere and the Northern Hemisphere, with the Northern Hemisphere dominating at the nightside magnetopause.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Astronomy & Astrophysics
A. Ramada C. Sukarmadji, Patrick Antolin, James A. McLaughlin
Summary: The recent study presents observations of nanojets in multiple coronal structures and environments, showing that they are accompanied by small nanoflare-like intensity bursts, have velocities of 150-250 km/s, occur transversely to the field line of origin, and have kinetic and thermal energies within the nanoflare range.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Yulei Wang, Xin Cheng, Mingde Ding, Zhaoyuan Liu, Jian Liu, Xiaojue Zhu
Summary: This paper reports a self-consistent high-resolution 3D magnetohydrodynamical simulation of turbulent magnetic reconnection within a flare current sheet and reveals some important dynamical features. The study finds that fragmented current patches of different scales are spontaneously generated with a well-developed turbulence spectrum at the current sheet, as well as at the flare loop-top region. The close coupling of tearing mode and Kelvin-Helmholtz instabilities plays a critical role in developing turbulent reconnection and in forming dynamical structures with synthetic observables in good agreement with realistic observations. This sophisticated modeling approach represents a paradigm shift from the traditional 2D model to a 3D turbulent reconnection model that unifies flare dynamical structures of different scales.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Pallavi Bhat, Muni Zhou, Nuno F. Loureiro
Summary: Recent numerical studies have shown the existence of inverse transfer of magnetic energy in 3D magnetically dominated turbulence, likely driven by magnetic reconnection. The scaling behavior is found to be similar between 2D and 3D cases. Furthermore, simulations also demonstrate an inverse transfer of magnetic energy in 3D when the magnetic field is subdominant to the flow, with the emergence of a dynamo effect.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
G. Q. Yan, F. S. Mozer, G. K. Parks, C. L. Cai, T. Chen, M. L. Goldstein, Y. Ren
Summary: Within a Kelvin-Helmholtz vortex at the duskside magnetopause, a substructure characterized by two flux enhancements of cold magnetosheath plasma in a background of hot magnetosphere plasma is observed. The substructure is accompanied by plasma transport across the magnetopause, and the transport region is found to split into two parts. The observations suggest that this secondary R-T instability within the K-H vortex can drive plasma transport across the magnetopause.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Xuanye Ma, Peter Delamere, Katariina Nykyri, Brandon Burkholder, Stefan Eriksson, Yu-Lun Liou
Summary: The Kelvin-Helmholtz instability driven by sheared flow between the magnetosheath and magnetospheric plasma plays a significant role in the solar-wind-magnetosphere coupling process, impacting energy, momentum, and mass transport. The study demonstrates the use of test particle simulations to bridge the gap between MHD scale and kinetic scale, providing insights into ion behavior and transport in the presence of the KH instability.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2021)
Article
Physics, Fluids & Plasmas
Jagannath Mahapatra, Arkaprava Bokshi, Rajaraman Ganesh, Abhijit Sen
Summary: The study investigates the magnetic island coalescence problem in the presence of inplane, parallel shear flows using a 2D Viscoresistive Reduced MagnetoHydroDynamic model. It is found that for shear flow length scales greater than the magnetic island size, the maximum reconnection rate decreases monotonically, while for scales smaller than the island size, a critical value is reached where the shear flow destabilizes the islands. Additionally, the study shows suppression of the Kelvin-Helmholtz instability in super-Alfvenic flows and the stabilizing influence of plasma circulation inside the islands in strong shear flow cases.
PHYSICS OF PLASMAS
(2021)
Article
Optics
I Tazes, S. Passalidis, E. Kaselouris, I Fitilis, M. Bakarezos, N. A. Papadogiannis, M. Tatarakis, V Dimitriou
Summary: This research focuses on the delivery of optically shaped targets through the interaction of nanosecond laser pulses with high-density gas-jet profiles, and the acceleration of protons in the near-critical density regime using magnetic vortex acceleration (MVA). Geometrical alternatives for delivering laser pulses into the gas target were explored to control the density profile. The efficiency of the proposed shaping method was demonstrated through computational and particle-in-cell simulations.
HIGH POWER LASER SCIENCE AND ENGINEERING
(2022)
Article
Astronomy & Astrophysics
Hirakjyoti Das, Sukanta Deb, Amiya Baruah
Summary: In this study, a new technique was introduced to calculate the optimal values of each particle in the Plummer density model, improving the accuracy of gravitational force calculations. Results showed that the errors in force calculations were lower than those estimated from previous studies and remained stable for various considerations of nearest neighboring particles (N-neigh). The adjusted expression of epsilon(lambda,i) exhibited less dependence on N-neigh in the Plummer sphere, remarkably improving both the accuracy and the stability of the gravitational force calculation.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
K. Bora, R. Bhattacharyya, P. K. Smolarkiewicz
Summary: This study extends the computational model EULAG-MHD by incorporating Hall magnetohydrodynamics (HMHD) to explore fast magnetic reconnection at the ion inertial length scale. The results show that magnetic reconnections onset significantly earlier in HMHD simulations, leading to the development of magnetic flux ropes and tubes in three-dimensional evolution.
ASTROPHYSICAL JOURNAL
(2021)
Article
Geosciences, Multidisciplinary
Yue Zhou, Jih-Hong Shue, Hiroshi Hasegawa, Jianyong Lu, Ming Wang, Hanxiao Zhang
Summary: Using data from the ARTEMIS spacecraft near the Moon, this study statistically analyzes the properties of Kelvin-Helmholtz (KH) waves and the thickness of initial velocity shear layers on the magnetopause at lunar distance. The results show that at lunar distance, the KH waves have a larger wavelength and thickness compared to those at near-Earth magnetopause. The ratio of wavelength to thickness at lunar distance exceeds the range predicted by the linear theory, indicating that the observed KH waves are not consistent with the fastest growing mode according to linear theory. This study provides insights into the generation and development of KH waves at lunar distance.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Physics, Fluids & Plasmas
T. K. M. Nakamura, K. A. Blasl, H. Hasegawa, T. Umeda, Y-H Liu, S. A. Peery, F. Plaschke, R. Nakamura, J. C. Holmes, J. E. Stawarz, W. D. Nystrom
Summary: Research on the observations and simulations of Kelvin-Helmholtz instability (KHI) during southward interplanetary magnetic field (IMF) periods reveals that KHI can bend the magnetopause current layer and excite Rayleigh-Taylor instability (RTI), causing high-density arms to penetrate the magnetospheric side. Additionally, the nonlinear growth phase of KHI induces lower-hybrid drift instability (LHDI), resulting in efficient plasma mixing across the magnetopause.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
K. A. Blasl, T. K. M. Nakamura, F. Plaschke, R. Nakamura, H. Hasegawa, J. E. Stawarz, Yi-Hsin Liu, S. Peery, J. C. Holmes, M. Hosner, D. Schmid, O. W. Roberts, M. Volwerk
Summary: In this study, observations from the MMS mission of the Kelvin-Helmholtz instability (KHI) at the dusk-flank magnetopause are presented. The results show the formation of surface waves and vortices, indicating their likely generation by the KH instability. Additionally, the observed electric field fluctuations are generated by the lower-hybrid drift instability excited by the density gradient at the edges of the surface waves.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
M. Hosner, R. Nakamura, T. K. M. Nakamura, D. Schmid, E. V. Panov, F. Plaschke
Summary: This study statistically examines the electric field fluctuations in the lower-hybrid frequency range of 61 dipolarization front (DF) events. The results show enhanced power in the electric field fluctuations for all observed events. The power can vary significantly between events and is observed for both high and low values of the perpendicular electron density or pressure gradient. The peak wave power within the DF often coincides with the steepest density gradient. Furthermore, the wave power correlates with the magnetic flux transport rate of the DFs.
PHYSICS OF PLASMAS
(2022)
Article
Astronomy & Astrophysics
T. K. M. Nakamura, K. A. Blasl, Y. -H. Liu, S. A. Peery
Summary: KH waves are frequently observed at the Earth's low-latitude magnetopause during periods of northward interplanetary-magnetic-field (IMF), and they are believed to efficiently transport solar wind plasmas into the magnetosphere. However, during southward IMF periods, the KH waves are less frequently observed and their contribution to solar wind transport is not well explored. Recent studies have detected KH wave signatures near the dusk-flank of the magnetopause during southward IMF. Analysis of simulations shows that the turbulence caused by the lower-hybrid drift instability (LHDI) disturbs the structure of the KH wave layer and effectively transports plasmas across the layer. The transport rate obtained is comparable or even larger than that predicted for northward IMF, suggesting that diffusive solar wind transport induced by KH waves may be active at the flank-to-tail magnetopause during southward IMF.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2022)
Article
Astronomy & Astrophysics
W. -l. Teh, T. K. M. Nakamura, S. Zenitani, T. Umeda, R. Nakamura
Summary: This study investigates the energy conversion process during the coalescence of magnetic islands using a two-dimensional kinetic simulation. The results reveal the presence of energy dynamo and energy dissipation during this process, which have a significant impact on particle acceleration. The simulated energy conversion signatures are also compared favorably with observed magnetic islands.
ASTROPHYSICAL JOURNAL
(2023)
Article
Physics, Fluids & Plasmas
T. K. M. Nakamura, W. -l. Teh, S. Zenitani, T. Umeda, M. Oka, H. Hasegawa, A. M. Veronig, R. Nakamura
Summary: Magnetic reconnection is a fundamental process that converts magnetic energy to plasma kinetic energy in collisionless plasmas. This study focuses on the coalescence of multiple magnetic islands and examines the spatial dimensions of the internal structures. It is found that the dimensions depend on the initial thickness of the current sheet and the number of coalescing islands. The study also discovers that the horizontal dimension controls the evolution time scale, while the vertical dimension affects the reconnection maturity and particle heating.
PHYSICS OF PLASMAS
(2023)
Article
Astronomy & Astrophysics
H. Hasegawa, R. E. Denton, K. Dokgo, K. -J Hwang, T. K. M. Nakamura, J. L. Burch
Summary: This study analyzes three flux transfer events (FTEs) and subsequent crossing of a reconnecting magnetopause current sheet (MPCS) observed by the Magnetospheric Multiscale spacecraft. The aim is to understand the generation mechanism of ion-scale magnetic flux ropes (ISFRs) and their relationship with electromagnetic energy conversion and kinetic processes. The results show that ISFRs can be generated through secondary reconnection in an electron-scale current sheet (ECS), and the FTEs also formed through the same secondary reconnection process. Observations also suggest complex magnetic topology and localized conversion of electromagnetic to electron energy in the ISFR.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Kyoung-Joo Hwang, Chih-Ping Wang, Katariina Nykyri, Hiroshi Hasegawa, Mark B. Tapley, James L. Burch, Stephen A. Fuselier, Jerry Goldstein, Kyunghwan Dokgo, Takuma Nakamura, Mikhail Sitnov, Xuanye Ma, Yu Lin, Xue Wang
Summary: About sixty years ago, it was proposed that the solar wind entry and changes in magnetospheric magnetic topology via dayside magnetic reconnection initiate the magnetospheric convection over the poles. On the other hand, the quasi-viscous interaction via Kelvin-Helmholtz waves/vortices was proposed to lead to the solar wind entry and magnetospheric convection. However, their relative efficiency and importance leave a lot of room for enhanced and quantitative understanding. Recent observations and simulations indicate the possibility of a causality between the flank-side dynamics and magnetotail current sheet stability.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2023)
Article
Geosciences, Multidisciplinary
K. A. Blasl, T. K. M. Nakamura, R. Nakamura, A. Settino, H. Hasegawa, Z. Voeroes, M. Hosner, D. Schmid, M. Volwerk, Owen W. Roberts, E. Panov, Yi-Hsin Liu, F. Plaschke, J. E. Stawarz, J. C. Holmes
Summary: This article presents observations of an electron-scale reconnecting current sheet in the mixing region along the trailing edge of a Kelvin-Helmholtz vortex. Consistencies between the observations and a realistic simulation indicate a temporal evolution of the observed electron-scale reconnection current sheet. The multi-scale and inter-process character of this event is important in understanding plasma mixing connected to the Kelvin-Helmholtz instability and the temporal evolution of electron-scale reconnection.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Physics, Fluids & Plasmas
J. L. Burch, K. J. Genestreti, S. V. Heuer, A. Chasapis, R. B. Torbert, D. J. Gershman, R. Bandyopadhyay, C. J. Pollock, W. H. Matthaeus, T. K. M. Nakamura, J. Egedal
Summary: On July 11, 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection region in the Earth's magnetospheric tail. This paper reports on the investigation of the conversion of electromagnetic energy to electron kinetic energy and the conversion of electron beam energy to electron thermal energy via pressure-strain interaction. The main result is that omnidirectional, compressive dissipation of electron energy dominates in the positive J center dot E region, and incompressive parallel dissipation dominates in the inflow region where J center dot E is small.
PHYSICS OF PLASMAS
(2023)