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S D Bale - One of the best experts on this subject based on the ideXlab platform.
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ion scale Electromagnetic Waves in the inner heliosphere
Astrophysical Journal Supplement Series, 2020Co-Authors: T A Bowen, Alfred Mallet, Jia Huang, Katja Klein, D Malaspina, M L Stevens, S D Bale, J W BonnellAbstract:Understanding the physical processes in the solar wind and corona which actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of coherent Electromagnetic Waves at ion scales suggests that linear cyclotron resonance and non-linear processes are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of coherent Waves in the first perihelion encounter of PSP demonstrates the presence of transverse Electromagnetic Waves at ion resonant scales which are observed in 30-50\% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is of order 20 seconds; however long duration wave events can exist without interruption on hour-long timescales. Though ion scale Waves are preferentially observed during intervals with a radial mean magnetic field, we show that measurement constraints, associated with single spacecraft sampling of quasi-parallel Waves superposed with anisotropic turbulence, render the measured quasi-parallel ion-wave spectrum unobservable when the mean magnetic field is oblique to the solar wind flow; these results imply that the occurrence of coherent ion-scale Waves is not limited to a radial field configuration. The lack of strong radial scaling of characteristic wave amplitudes and duration suggests that the Waves are generated {\em{in-situ}} through plasma instabilities. Additionally, observations of proton distribution functions indicate that temperature anisotropy may drive the observed ion-scale Waves.
Gert Brodin - One of the best experts on this subject based on the ideXlab platform.
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resonant interaction between gravitational Waves Electromagnetic Waves and plasma flows
Physical Review D, 2003Co-Authors: Martin Servin, Gert BrodinAbstract:Gravitational Waves and Electromagnetic Waves are important as carriers of energy and information. This thesis is devoted to the study of the propagation and interaction of these Waves in plasmas, with emphasis on nonlinear effects and applications within astrophysics.The physical systems are described by the Einstein-Maxwell-fluid equations or Einstein-Maxwell-Vlasov equations, when a kinetic treatment is required. The small amplitude and high-frequency approximation is employed for the gravitational Waves, such that perturbative techniques can be applied and space-time can be considered locally flat, with a gravitational radiation field superimposed on it. The gravitational Waves give rise to coupling terms that have the structure of effective currents in the Maxwell equations and an effective gravitational force in the equation of motion for the plasma. The Einstein field equations describe the evolution of the gravitational Waves, with the perturbed energy-momentum density of the plasma and the Electromagnetic field as a source.The processes that are investigated are gravitational Waves exciting Electromagnetic Waves in plasmas, altering the optical properties of plasmas and accelerating charged particles. The thesis also deals with the propagation propertities of gravitational and Electromagnetic Waves, e.g. effects due to resonant wave-particle interactions, plasma inhomogeneties and nonlinear self-interactions. It is also shown that plasmas that are not in thermodynamical equilibrium may release their free energy by emitting gravitational Waves.
J W Bonnell - One of the best experts on this subject based on the ideXlab platform.
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ion scale Electromagnetic Waves in the inner heliosphere
Astrophysical Journal Supplement Series, 2020Co-Authors: T A Bowen, Alfred Mallet, Jia Huang, Katja Klein, D Malaspina, M L Stevens, S D Bale, J W BonnellAbstract:Understanding the physical processes in the solar wind and corona which actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of coherent Electromagnetic Waves at ion scales suggests that linear cyclotron resonance and non-linear processes are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of coherent Waves in the first perihelion encounter of PSP demonstrates the presence of transverse Electromagnetic Waves at ion resonant scales which are observed in 30-50\% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is of order 20 seconds; however long duration wave events can exist without interruption on hour-long timescales. Though ion scale Waves are preferentially observed during intervals with a radial mean magnetic field, we show that measurement constraints, associated with single spacecraft sampling of quasi-parallel Waves superposed with anisotropic turbulence, render the measured quasi-parallel ion-wave spectrum unobservable when the mean magnetic field is oblique to the solar wind flow; these results imply that the occurrence of coherent ion-scale Waves is not limited to a radial field configuration. The lack of strong radial scaling of characteristic wave amplitudes and duration suggests that the Waves are generated {\em{in-situ}} through plasma instabilities. Additionally, observations of proton distribution functions indicate that temperature anisotropy may drive the observed ion-scale Waves.
Martin Servin - One of the best experts on this subject based on the ideXlab platform.
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resonant interaction between gravitational Waves Electromagnetic Waves and plasma flows
Physical Review D, 2003Co-Authors: Martin Servin, Gert BrodinAbstract:Gravitational Waves and Electromagnetic Waves are important as carriers of energy and information. This thesis is devoted to the study of the propagation and interaction of these Waves in plasmas, with emphasis on nonlinear effects and applications within astrophysics.The physical systems are described by the Einstein-Maxwell-fluid equations or Einstein-Maxwell-Vlasov equations, when a kinetic treatment is required. The small amplitude and high-frequency approximation is employed for the gravitational Waves, such that perturbative techniques can be applied and space-time can be considered locally flat, with a gravitational radiation field superimposed on it. The gravitational Waves give rise to coupling terms that have the structure of effective currents in the Maxwell equations and an effective gravitational force in the equation of motion for the plasma. The Einstein field equations describe the evolution of the gravitational Waves, with the perturbed energy-momentum density of the plasma and the Electromagnetic field as a source.The processes that are investigated are gravitational Waves exciting Electromagnetic Waves in plasmas, altering the optical properties of plasmas and accelerating charged particles. The thesis also deals with the propagation propertities of gravitational and Electromagnetic Waves, e.g. effects due to resonant wave-particle interactions, plasma inhomogeneties and nonlinear self-interactions. It is also shown that plasmas that are not in thermodynamical equilibrium may release their free energy by emitting gravitational Waves.
P. Kaufmann - One of the best experts on this subject based on the ideXlab platform.
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simulating the emission of Electromagnetic Waves in the terahertz range by relativistic electron beams
Astronomy and Astrophysics, 2006Co-Authors: J. -i. Sakai, Yuya Nagasugi, S. Saito, P. KaufmannAbstract:Aims. We investigate the dynamics of relativistic electron beams propagating along a uniform magnetic field and the emission process of Electromagnetic Waves within the terahertz range from the solar photosphere. Our aim is to understand a new solar burst component emitting only in the terahertz range during the solar flare observed by Kaufmann et al. (2004). Methods. We used a 2D3V fully relativistic Electromagnetic particle-in-cell (PIC) simulation. Results. We did three different kinds of simulations. The first simulation confirmed that the growth rate of relativistic electron beam instability agrees well with the theoretical estimation. From the second simulation of the electron beam with finite width, we found that the beams are confined along the magnetic field and the Electromagnetic Waves are generated forward of the electron beams. Some fraction of the electrons are accelerated more than the initial beam velocity. From the third simulation where the electron beams propagate into the high density region, we found that strong Electromagnetic Waves are generated backward to the electron beams. We also found that the higher frequency emission like 405 GHz, which originate in the strong magnetic field region, becomes stronger than the 212 GHz emission, as shown in the observation by Kaufmann et al. (2004). These simulation results could be applied to the Electromagnetic wave emission from the solar photosphere during the solar flares.
