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)
Article
Physics, Multidisciplinary
Joonas Nattila, Andrei M. Beloborodov
Summary: Magnetic energy around astrophysical compact objects can exceed plasma mass and energize the plasma through magnetic turbulence, but particle acceleration is not efficient.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
David M. Malaspina, Alexandros Chasapis, Peter Tatum, Chadi Salem, Stuart D. Bale, John W. Bonnell, Thierry Dudok de Wit, Keith Goetz, Marc Pulupa, Jasper Halekas, Phyllis Whittlesey, Roberto Livi, Anthony W. Case, Michael L. Stevens, Davin Larson
Summary: Intense electromagnetic, broadband plasma waves identified as kinetic Alfven waves (KAWs) are reported in the near-Sun solar wind. These KAWs are found to be spatially inhomogeneous, occurring preferentially where the ambient magnetic field experiences strong deviations from the Parker spiral direction.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
David B. Wexler, Michael L. Stevens, Anthony W. Case, Paul Song
Summary: The study discusses the Alfven radius and angular momentum in solar wind, using data from the Parker Solar Probe for measurements. The calculated Alfven speeds were estimated under specific conditions, confirming recent research findings.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Astronomy & Astrophysics
M. Pelekhata, K. Murawski, S. Poedts
Summary: Large-amplitude two-fluid Alfven waves can significantly contribute to the heating of the solar chromosphere and the generation of plasma outflows.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Geochemistry & Geophysics
Qi Zhaohui, Liu Yong, Liu Ruoyan
Summary: Research has shown that the origin of small coronal hole winds and Alfvenic slow winds may intertwine and exhibit different characteristics during propagation. This study provides new insights into solving the mystery of the origin of the slow solar wind.
CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION
(2021)
Article
Astronomy & Astrophysics
F. S. Mozer, O. V. Agapitov, J. C. Kasper, R. Livi, O. Romeo, I. Y. Vasko
Summary: The aim of this study is to determine the perpendicular and parallel proton heating rates in the solar wind. By removing the speed dependence, the perpendicular and parallel temperatures of protons were compared to the radial dependence. Perpendicular heating of protons was observed between 20 and 160 solar radii, while there was no heating or cooling of parallel protons below 70 solar radii. The heating rates that produced the perpendicular temperatures were estimated at different distances from the Sun.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Energy & Fuels
Ti Zilong, Deng Xiao Wei
Summary: This study introduces a novel coupling approach considering the impact of inhomogeneous wave loads on monopile-supported wind turbines in wind farm layout optimization.
By optimizing the layout, the total wave load of the wind farm can be minimized while maintaining a favorable annual energy production.
Experimental results show that the coupling optimization has significant benefits in reducing wave loads by 20.1%-40.5% while still preserving a favorable amount of AEP.
Article
Physics, Fluids & Plasmas
Feiyu Li, Xiangrong Fu, Seth Dorfman
Summary: This study takes an important step towards direct hybrid simulation of the Alfven wave parametric decay instability (PDI) in a laboratory plasma. The threshold behaviors of Alfven wave amplitude and frequency required for triggering the instability are identified with the help of simulations and supported by simple theoretical analysis.
PHYSICS OF PLASMAS
(2022)
Article
Astronomy & Astrophysics
Rohit Chhiber, William H. Matthaeus, Arcadi Usmanov, Riddhi Bandyopadhyay, Melvyn L. Goldstein
Summary: Motivated by theoretical, numerical, and observational evidence, this study explores the possibility that the critical transition between sub-Alfvenic flow and super-Alfvenic flow in the solar atmosphere takes place within fragmented subvolumes. The initial observations could not provide enough evidence to distinguish between this possibility and a folded surface separating simply connected regions. However, future observations may help differentiate between the two possibilities. A global magnetohydrodynamic model coupled with a turbulence transport model is used to generate possible realizations of this critical zone.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Thermodynamics
Biao Lei, Zhong-Jie Duan, Yu-Ting Wu
Summary: The paper introduces a new integrated heat pump system that combines vapor compression heat pump and absorption heat pump to achieve continuous and stable heating in low temperature environment with low energy consumption.
ENERGY CONVERSION AND MANAGEMENT
(2022)
Article
Green & Sustainable Science & Technology
Huadong Huang, Shiquan Shan, Zhijun Zhou
Summary: A novel solar concentrating photovoltaic and near-field thermophotovoltaic hybrid system is proposed to achieve efficient solar power generation. The efficiency of the hybrid system exceeds the maximum efficiency of future solar thermophotovoltaic systems, and the optimal concentration ratio for practical application is 1000, with an efficiency of 56.20%.
Article
Astronomy & Astrophysics
S. A. Belov, S. Vasheghani Farahani, N. E. Molevich
Summary: The aim of this study is to investigate the effects of thermal misbalance on the behavior of Alfven waves in solar active regions. The study provides a description of the non-linear forces associated with Alfven waves in non-ideal conditions and their influence on the boundary of thin magnetic structures in thermally active plasmas. The results show that the effects of thermal misbalance are stronger for shear Alfven waves compared to torsional Alfven waves.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
B. van der Holst, J. Huang, N. Sachdeva, J. C. Kasper, W. B. Manchester, D. Borovikov, B. D. G. Chandran, A. W. Case, K. E. Korreck, D. Larson, R. Livi, M. Stevens, P. Whittlesey, S. D. Bale, M. Pulupa, D. M. Malaspina, J. W. Bonnell, P. R. Harvey, K. Goetz, R. J. MacDowall
Summary: In this study, the authors improved their simulations and achieved better agreement with PSP data. The simulations suggest that the solar wind near the perihelion of PSP may originate from a negative-polarity region near the equator.
ASTROPHYSICAL JOURNAL
(2022)
Article
Physics, Multidisciplinary
Jyotsna Sharma, Siddhartha Singh, Amit Kumar, Md. Amzad Hossain, Shaik Hasane Ahammad, Ahmed Nabih Zaki Rashed
Summary: The excitation of shear Alfven waves through the parametric degeneration of lower hybrid waves in complex plasma is investigated. The lower hybrid wave disintegrates into a low-frequency shear Alfven wave mode and a lower hybrid sideband mode when the electron oscillatory velocity in the plasma is a few percent of the sound velocity. The analysis shows that the shear Alfven wave mode is initiated by the lower hybrid sideband mode and the lower hybrid pump wave through the application of a ponderomotive force. The presence of dust grains in the plasma impacts this instability, and the growth rate increases with axial wave number, oscillatory velocity and amplitude of pump waves, and relative density, while it decreases with an increase in the applied magnetic field. The magnetic field related to the shear Alfven wave is crucial for anomalous diffusion and these theoretical results can explain the behavior of tokamak plasmas in the presence of dust.
BRAZILIAN JOURNAL OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
L. Ofman, T. E. Moore, A. Glocer
PLANETARY AND SPACE SCIENCE
(2019)
Article
Astronomy & Astrophysics
Leon Ofman
Article
Astronomy & Astrophysics
L. Ofman, A. Koval, L. B. Wilson, A. Szabo
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2019)
Article
Astronomy & Astrophysics
R. E. Denton, L. Ofman, Y. Y. Shprits, J. Bortnik, R. M. Millan, C. J. Rodger, C. L. da Silva, B. N. Rogers, M. K. Hudson, K. Liu, K. Min, A. Glocer, C. Komar
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2019)
Article
Astronomy & Astrophysics
Jie Zhao, Sarah E. Gibson, Silvano Fineschi, Roberto Susino, Roberto Casini, Steven R. Cranmer, Leon Ofman, Hui Li
Summary: In ultraviolet spectropolarimetric observations of the solar corona, the impact of magnetic fields, solar wind velocity, and temperature anisotropies on linear polarization direction rotation is studied. Different effects operate differently in distinct spatial regimes, which opens up the possibility for using linear polarization measurements in UV lines to diagnose important physical characteristics of the solar corona.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
L. Ofman, L. B. Wilson, A. Koval, A. Szabo
Summary: Research shows that alpha particles have a significant impact on the dynamics, oscillations, and structure of high Mach number heliospheric shocks, potentially leading to nonstationarity and shock-front rippling.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Leon Ofman, Tongjiang Wang
Summary: In this study, a three-dimensional magnetohydrodynamic (MHD) model was used to simulate the excitation and dissipation of slow magnetosonic waves in hot flaring coronal loops based on observational data. The results showed significant leakage of the waves from the hot loops, with a small effect of viscous dissipation in cooler loops and more significant effects in hotter loops. These findings highlight the importance of nonlinear 3D MHD models in understanding the various wave couplings, damping, and viscous dissipation in hot flaring coronal loops.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Leon Ofman, Amir Averbuch, Adi Shliselberg, Idan Benaun, David Segev, Aron Rissman
Summary: A novel AI technique combining multiple algorithms is applied to NASA's TESS dataset to identify exoplanetary candidates, resulting in the discovery of new candidates and demonstrating successful automated classification of TCEs.
Article
Astronomy & Astrophysics
Leon Ofman, Scott A. Boardsen, Lan K. Jian, Jaye L. Verniero, Davin Larson
Summary: Recent observations from the Parker Solar Probe (PSP) mission show evidence of ion beams, temperature anisotropies, and kinetic wave activity in the inner heliosphere near perihelia. Researchers use models and observations to conclude that ion beam driven kinetic instabilities play an important role in the heating process of the solar wind plasma.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Leon Ofman, Therese A. Kucera, C. Richard DeVore
Summary: We investigate the properties of nonlinear fast magnetosonic (NFM) waves in a solar prominence and model them using a three-dimensional magnetohydrodynamics (3D MHD) model. The model includes the structure of the prominence pillar and the effects of mode coupling and density compressions associated with NFM waves. We demonstrate the dynamic effects of the Lorentz force on the pillar structure and wave propagation in a non-force-free field. The insights gained from the 3D MHD modeling improve our understanding of fast MHD wave activity in prominence structures.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Sripan Mondal, Abhishek K. Srivastava, Sudheer K. Mishra, K. Sangal, Pradeep Kayshap, Yang Guo, David Pontin, Vadim M. Uritsky, Leon Ofman, Tongjiang Wang, Ding Yuan
Summary: Multiwavelength observations of propagating disturbances (PDs) were analyzed to determine their driving mechanism and physical nature. The observations revealed the merging of magnetic strands in the corona, followed by brightening and propagation in a cusp-shaped magnetic channel. Analysis of the magnetic field showed the presence of magnetic nulls and quasi-separatrix layers (QSLs), indicating magnetic reconnection. Spectroscopic analysis showed mass motion in the observed region. The observed PDs were described as quasiperiodic plasma flows generated by periodic reconnection near a coronal magnetic null.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Leon Ofman, Therese A. Kucera
ASTROPHYSICAL JOURNAL
(2020)
Article
Astronomy & Astrophysics
Wei Liu, Meng Jin, Cooper Downs, Leon Ofman, Mark C. M. Cheung, Nariaki V. Nitta
ASTROPHYSICAL JOURNAL LETTERS
(2018)
Article
Astronomy & Astrophysics
Tongjiang Wang, Leon Ofman, Xudong Sun, Sami K. Solanki, Joseph M. Davila
ASTROPHYSICAL JOURNAL
(2018)
Article
Astronomy & Astrophysics
Leon Ofman, Wei Liu
ASTROPHYSICAL JOURNAL
(2018)