Article
Astronomy & Astrophysics
K. C. Barik, S. Singh, G. S. Lakhina
Summary: A theoretical model discusses the resonant instability of kinetic Alfven waves (KAWs) driven by ion beam and how non-Maxwellian kappa-electrons impede the growth of KAWs. The model also examines the effects of other plasma parameters on wave excitation and can generate waves with frequencies relevant to auroral ionospheric altitudes. Predictions from the model are applicable to planetary environments with ion beams and non-Maxwellian kappa-electrons.
ASTROPHYSICAL JOURNAL
(2021)
Article
Physics, Fluids & Plasmas
Run Shi, Jun Liang
Summary: This study examines the possible mode conversion from kinetic Alfven wave to modified electron acoustic wave using a multi-fluid model. The results indicate that such conversion is ubiquitous in regions with steep electron temperature gradients, such as planetary auroral acceleration regions or the boundary of the solar corona.
PHYSICS OF PLASMAS
(2022)
Article
Astronomy & Astrophysics
K. C. Barik, S. V. Singh, G. S. Lakhina
Summary: The generation of kinetic Alfven waves (KAWs) is studied through a three-component theoretical model considering ion beam and velocity shear as sources of free energy. The model incorporates Maxwellian distributed background ions, drifting-Maxwellian beam ions, and kappa-electrons. The study finds that combinations of positive velocity shear with counter-streaming beam ions or parallel streaming beam ions with negative velocity shear favor the excitation of KAWs. The effects of the kappa-parameter and plasma parameters on the excitation of KAWs are explored.
ASTROPHYSICAL JOURNAL
(2023)
Article
Multidisciplinary Sciences
Muni Zhou, Zhuo Liu, Nuno F. Loureiro
Summary: We conducted analytical and numerical investigations on subion-scale turbulence in low-beta plasmas using a rigorous reduced kinetic model. The results show that electron heating is primarily caused by Landau damping of kinetic Alfven waves rather than Ohmic dissipation. This collisionless damping is facilitated by the weakening of advective nonlinearities near intermittent current sheets, where free energy concentrates. The linearly damped energy of electromagnetic fluctuations explains the steepening of their energy spectrum compared to a fluid model.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Letter
Physics, Fluids & Plasmas
Liu Chen, Zhiyong Qiu, Fulvio Zonca
Summary: This paper demonstrates that the parametric decay instabilities of kinetic Alfven waves in a nonuniform plasma can be significantly different from those in a uniform plasma. The decay rate via ion Compton scattering is found to be enhanced by an order of magnitude, and the parity of the decay kinetic Alfven wave spectrum is broken, resulting in finite net wave momentum transfer and significant plasma transport.
PHYSICS OF PLASMAS
(2022)
Article
Astronomy & Astrophysics
A. A. Fayad, W. M. Moslem, H. Fichtner, M. Lazar
Summary: Space observations reveal that Venus experiences significant atmospheric erosion due to solar wind. Plasma acceleration, particularly the kinetic Alfven waves (KAW), is proposed as a possible mechanism for charged particle energization in the upper atmosphere of Venus. Various parameters such as ionic concentration, solar wind electron temperature, magnetic field strength, and obliqueness influence the structures and electric field of the solitary KAWs.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Geosciences, Multidisciplinary
A. J. Hull, P. A. Damiano, C. C. Chaston, J. R. Johnson, G. D. Reeves
Summary: This study investigates the properties of traveling kinetic Alfven waves (KAWs) and their role in energizing electrons in the inner magnetosphere during a geomagnetic storm. The results demonstrate the crucial importance of cold electrons for reproducing observed distributions.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
Yangyang Shen, Anton V. Artemyev, Xiao-Jia Zhang, Ying Zou, Vassilis Angelopoulos, Ivan Vasko, Andrei Runov, Ethan Tsai, Colin Wilkins
Summary: Energetic electron precipitation from the magnetosphere to the ionosphere during substorms is important for magnetosphere-ionosphere coupling. Through observations and analysis, it was found that wave-particle interactions are likely responsible for the precipitation of energetic electrons from the plasma sheet. Kinetic Alfven waves were found to dominate over whistler-mode waves in scattering and precipitating energetic plasma sheet electrons during the substorm injection.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Physics, Multidisciplinary
Kuldeep Singh, Gursirat Singh, N. S. Saini
Summary: This paper investigates the formation and dynamics of periodic and solitary kinetic Alfven waves in nonthermal electron-positron-ion plasma. The KdV equation is derived using the reductive perturbation technique, and the Sagdeev potential and Hirota bilinear methods are applied to examine the wave dynamics. The study reveals that the plasma beta, positron density, propagation angle, and nonthermality of electrons and positrons have a significant influence on the behavior of the waves.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
A. S. Leonovich, D. A. Kozlov, A. A. Vlasov
Summary: This study examines the spatial structure of kinetic Alfven waves near a dissipative layer, exploring the changes in dispersion type and phase shifts in the wave characteristics. The absorption of Alfven wave energy in the dissipative layer can lead to the formation of electron fluxes and stable auroral red arcs. An analytical formula is proposed for determining the density of the electron flux toward the ionosphere and the flux of the energy transferred by them.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Physics, Fluids & Plasmas
Alfred Mallet, Benjamin D. G. Chandran
Summary: The study demonstrates that large-amplitude, non-planar Alfven-wave packets are exact nonlinear solutions of the relativistic magnetohydrodynamic equations when the total magnetic-field strength in the local fluid rest frame is constant. These constant-b AWs propagate without distortion at the relativistic Alfven velocity and never steepen into shocks, suggesting their presence in relativistic outflows around compact astrophysical objects.
JOURNAL OF PLASMA PHYSICS
(2021)
Article
Geosciences, Multidisciplinary
Jiwon Choi, Dong-Hun Lee
Summary: Standing poloidal Alfven waves are excited by wave-particle interaction in the magnetosphere, with ultralow frequency radial oscillations. Through magnetohydrodynamic simulations, it has been shown that the long-lasting poloidal waves depend on the local Alfven frequency gradient being negligible. Two necessary conditions for the existence of persistent poloidal modes have been derived, which are consistent with statistical observations.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Astronomy & Astrophysics
N. Villarroel-Sepulveda, R. A. Lopez, P. S. Moya
Summary: By studying the dispersion properties of Alfvenic waves in plasmas with different heavy ion populations, it is found that the inclusion of oxygen ions can significantly reduce the transition angle from EMIC to KAW mode and increase the damping in certain wavenumber regions.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Computer Science, Interdisciplinary Applications
Claudia Tugulan, Olga Trichtchenko, Emilian Parau
Summary: This work presents three-dimensional, nonlinear traveling wave solutions for water waves under a sheet of ice, specifically flexural-gravity waves. The ice is modeled as a thin elastic plate on top of water with infinite depth, and the equations are formulated using a boundary integral method. Depending on the velocity of the moving disturbance generating the flow, different deflection patterns of the floating ice sheet are observed. A novel hybrid preconditioning technique is introduced to efficiently compute solutions, which significantly increases grid refinement and decreases computational time compared to existing methods. The approach is demonstrated to be applicable to three-dimensional ice wave patterns in different velocity regimes.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Physics, Applied
Ye Jeong Shin, Hong Min Seung, Joo Hwan Oh
Summary: What makes elastic waves different from other waves is the existence of various wave modes and coupling between these modes. In this study, fluid-like elastic metasurfaces were proposed to perfectly eliminate mode coupling. Strip-type unit cells were used to design and realize elastic metasurfaces mimicking acoustic hard-wall and soft-wall. Numerical analysis and experiments were conducted to prove the validity of the designed unit cells. This study presents a more versatile metasurface by solving the mode coupling of solid elastic waves, and the designed fluid-like metasurfaces can be further utilized in studies considering the opposite phase shift characteristic.
APPLIED PHYSICS LETTERS
(2023)
Article
Geosciences, Multidisciplinary
K. Nykyri, J. Johnson, E. Kronberg, D. Turner, S. Wing, I Cohen, K. Sorathia, X. Ma, B. Burkholder, G. Reeves, J. Fennell
Summary: This study demonstrates the first observations of counter-streaming energetic electrons and trapped energetic protons in the high-latitude magnetosphere, likely originating from large diamagnetic cavities created by magnetic reconnection.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Astronomy & Astrophysics
E. - H. Kim, J. R. Johnson, K. Nykyri
Summary: The Kelvin-Helmholtz instability of magnetohydrodynamic surface waves at the low latitude boundary layer is examined using both an eigenfrequency analysis and a time-dependent wave simulation. The results show the occurrence of unstable KH waves under certain conditions, and the coupling between the secondary KH waves and resonant surface Alfven waves driven by the sheared flow. There are notable differences between the primary and secondary KH waves.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2022)
Article
Astronomy & Astrophysics
Simon Wing, Jay R. Johnson, Drew L. Turner, Aleksandr Y. Ukhorskiy, Alexander J. Boyd
Summary: Many solar wind parameters correlate with each other, making it challenging to study the cause-and-effect relationship between solar wind and magnetosphere. By using conditional mutual information, the effect of individual solar wind and magnetospheric drivers on radiation belt electrons can be isolated. It is found that solar wind density negatively correlates with electron phase space density, and the effect of solar wind velocity shifts the time scale for this process. The peak correlation between solar wind velocity and electron phase space density suggests a time scale for electron acceleration.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Geosciences, Multidisciplinary
A. J. Hull, P. A. Damiano, C. C. Chaston, J. R. Johnson, G. D. Reeves
Summary: This study investigates the properties of traveling kinetic Alfven waves (KAWs) and their role in energizing electrons in the inner magnetosphere during a geomagnetic storm. The results demonstrate the crucial importance of cold electrons for reproducing observed distributions.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
Simon Wing, Drew L. Turner, Aleksandr Y. Ukhorskiy, Jay R. Johnson, Thomas Sotirelis, Romina Nikoukar, Giuseppe Romeo
Summary: An empirical model of radiation belt relativistic electrons is developed, with inputs of solar wind and magnetospheric parameters and outputs of radiation belt electron phase space density. The model is constructed using neural networks assisted by information theory and can be used to forecast the phase space density of radiation belt electrons 30-60 minutes in advance.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Article
Astronomy & Astrophysics
Sung-Jun Noh, Hyomin Kim, Marc Lessard, Mark Engebretson, Vyacheslav Pilipenko, Eun-Hwa Kim, Jay Johnson, Ilya Kuzichev, Michelle Salzano
Summary: In this study, we investigated the characteristics of EMIC wave propagation and filtering from the source region to the ground. The study utilized magnetometers aboard GOES 13 and the SNK station in northern Canada to obtain simultaneous observations. The results revealed differences in wave properties and environmental factors between coincident and non-coincident wave events.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Drew Coffin, Peter Damiano, Peter Delamere, Jay Johnson, Chung-Sang Ng
Summary: This study investigates the origin of electron energization at high latitudes of Jupiter through simulating the propagation of dispersive Alfven waves, and quantifies the impact of these waves on electron energization. It successfully generates electron populations consistent with observations, shedding light on the energy budget of the torus and Io-related auroral emissions.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
S. Wing, M. F. Thomsen, J. R. Johnson, D. G. Mitchell, R. C. Allen, X. Ma, P. A. Delamere
Summary: The inward plasma transport in the Saturnian magnetosphere is investigated using a formalism called flux tube interchange stability developed by Southwood & Kivelson. Seven events were selected to analyze three different cases. The results indicate that the flux tube should be moving inward and the entropy of the flux tube plays an important role in braking the plasma inward transport.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Elmer C. Rivera, Jay R. Johnson, Jonathan Homan, Simon Wing
Summary: This study reveals that solar flares exhibit memory on different timescales and demonstrate clustering behavior, with higher likelihood of flare recurrence on shorter timescales.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
X. Ma, P. A. Delamere, A. Schok, S. Wing, J. R. Johnson, Yu-Lun Liou
Summary: The interaction between the solar wind and giant magnetospheres is crucial for magnetospheric physics, with the Kelvin-Helmholtz instability playing a significant role in the low-latitude dawn side flank region of Jupiter. The occurrence of this instability can modify the magnetopause boundary layer, as confirmed by the observations from Juno's mission.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Elmer C. Rivera, Jay R. Johnson, Jonathan Homan, Simon Wing
Summary: Discrete dynamic systems can be accurately described and reconstructed by analyzing the time intervals between discrete events. Research on the waiting time between stellar flares in Sun-like stars' light curves shows that low amplitude enhancements, which were previously considered random noise, actually contain valuable information similar to solar flares. Mutual information analysis can be used to identify a threshold that maximizes the information content of flare sequences, enabling the extraction of more flare information from stellar light curves.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Geosciences, Multidisciplinary
Eun-Hwa Kim, Jay R. R. Johnson
Summary: We use the advanced full-wave simulation code Petra-M to examine the coupling of solar wind fluctuations with electromagnetic ion cyclotron (EMIC) waves in the magnetosphere. The dipole tilt has a dramatic effect on the coupling process, with a tilted dipole field increasing the efficiency of coupling. Solar wind fluctuations incident at high magnetic latitude effectively reach the ground along the field line and mode-convert to linearly polarized field-aligned propagating waves at the Alfven and IIH resonances. Therefore, solar wind compressions efficiently drive linearly polarized EMIC waves when the dipole angle is tilted toward or away from the Sun-Earth direction.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Astronomy & Astrophysics
Jay R. Johnson, Simon Wing, Carson O'ffill, Bishwa Neupane
Summary: Information theory is used to characterize the periodicities and memories of solar active regions. An innovative method based on image entropy is developed to track and measure the information flow between consecutive images. The study reveals long-term memory, a coherence time of 2 years, and the average size of active region structures carrying the most information. The findings have implications for predictability and flux transport in the Sun, and the method can be applied to other stellar data.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Geosciences, Multidisciplinary
P. A. Damiano, P. A. Delamere, E. -H. Kim, J. R. Johnson, C. S. Ng
Summary: Juno satellite observations have shown significant levels of electron energization, reaching up to 10⁵-10⁶ eV. To explain these observations, a hybrid gyrofluid kinetic-electron model is used in an untilted dipolar topology, illustrating high energization in weak current conditions through inertial Alfven waves close to the Jupiter ionosphere. This is achieved with ambient plasma densities and magnetic field perturbations inferred from Juno satellite data. The key factor enabling the high energization is the extremely low densities observed, requiring the acceleration of electrons to very high velocities to carry the field-aligned current.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geochemistry & Geophysics
A. A. Schok, P. A. Delamere, B. Mino, P. A. Damiano, B. Zhang, A. Sciola, K. Sorathia, S. Wing, J. R. Johnson, X. Ma, Z. Yao, O. Brambles
Summary: By analyzing the magnetic field and particle data from the Juno spacecraft, researchers have discovered a highly structured plasmadisc within Jupiter's magnetosphere, which is magnetically connected to the high-latitude polar region. This finding is crucial for understanding the overall structure and dynamics of Jupiter.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2023)
