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Dispersion relation for large amplitude circularly polarized plane wave propagation along magnetic field in hot collision-free plasma, considering distribution function
The stability of a semiinfinite quasi-neutral inhomogeneous plasma with magnetic viscosity has been discussed by using JWKB approximation in which the parameters are regarded slowing varying. Dispersion relation is obtained and discussed. It is found that the inhomogeneous system is unstable for all perturbations with k(y) = 0. A dispersion relation for homogeneous plasma is also obtained and discussed. It is shown that fast and slow-MHD waves propagate in the homogeneous plasma in the limit of almost perpendicular propagation under certain conditions.
This report walks through the process of deriving the wave equation for a vertical wave being propagated through a spatially varying plasma in a vertical magnetic field. Additionally, this report shows how to derive the index of refraction of the plasma corresponding to three different modes of the vertical magnetic field. Finally, this paper briefly explores the next steps planned to successfully simulate and test the equations in a pre-existing phase screen scintillation code.
This report summarizes results obtained through the support of NASA Grant NAGW-2412. The objective of this project is to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as if flew by Neptune. This study has included data analysis, theoretical and numerical calculations, ray tracing, and modeling to determine the possible source mechanism(s) and locations of the Neptune radio emissions. We have completed four papers, which are included in the appendix. The paper 'Modeling of Whistler Ray Paths in the Magnetosphere of Neptune' investigated the propagation and dispersion of lighting-generated whistler in the magnetosphere of Neptune by using three dimensional ray tracing. The two papers 'Numerical Simulations of Bursty Radio Emissions from Planetary Magnetospheres' and 'Numerical Simulations of Bursty Planetary Radio Emissions' employed numerical simulations to investigate an alternate source mechanism of bursty radio emissions in addition to the cyclotron maser instability. We have also studied the possible generation of Z and whistler mode waves by the temperature anisotropic beam instability and the result was published in 'Electron Cyclotron Wave Generation by Relativistic Electrons.' Besides the aforementioned studies, we have also collaborated with members of the PRA team to investigate various aspects of the radio wave data. Two papers have been submitted for publication and the abstracts of these papers are also listed in the appendix.
The purpose of this project was to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as it flew by Neptune. The study has included data analysis, theoretical and numerical calculations, and ray tracing to determine the possible source mechanisms and locations of the radiation, including the narrowband bursty and smooth components of the Neptune radio emission.
We consider the power coupled to the plasma from a cylindrical source emitting resonance cones, propagative slow waves which exist in low density magnetized plasmas when the signs of the Stix parameters S and P differ. In this work, we calculate this power for the first time for any collisionality, and show that it remains finite in the cold collisionless limit, even as the radiofrequency electric field itself, and the associated power absorption density, is singular. We give the main parameter dependencies of the coupled power.
Space measurements have provided a wealth of data on wave phenomena, plasma parameters, and energetic particle characteristics within the earth's magnetosphere. In the present paper, the generation, propagation, and interaction of plasma waves are discussed, along with the interpretation of the observations. Data on plasma waves from other planetary magnetospheres and cosmic plasma systems are examined and interpreted by analogy to the earth's magnetosphere. Areas requiring continued plasma wave research are indicated.
A nonlinear plasma theory for self-modulation of pulsar radio pulses is discussed. A nonlinear Schroedinger equation is derived for strong electromagnetic waves propagating in an electron-positron plasma. The nonlinearities arising from wave-intensity-induced particle-mass variation may excite the modulational instability of circularly and linearly polarized pulsar radiation. The resulting wave envelopes can take the form of periodic wave trains or solitons. These nonlinear stationary waveforms may account for the formation of pulsar microstructures.
Plasma effects on electromagnetic wave propagation during Apollo spacecraft reentry from lunar missions
New steady-state solutions are derived which describe electromagnetic waves strong enough to make plasma ions and electrons relativistic. A two-fluid model is used throughout. The following solutions are studied: (1) linearly polarized waves with phase velocity much greater than c; (2) arbitrarily polarized waves with phase velocity near c, in a cold uniform plasma; (3) circularly polarized waves in a uniform plasma characterized by a scalar pressure tensor. All of these waves are capable of propagating in normally overdense plasmas, due to nonlinearities introduced by relativistic effects. The propagation of relativistically strong waves in a density gradient is examined, for the example of a circularly polarized wave strong enough to make electrons but not ions relativistic. It is shown that such a wave propagates at constant energy flux despite the nonlinearity of the system.
Electrodynamics of moving anisotropic media with velocities small compared to light, emphasizing plane wave propagation in drifting magnetoionic plasma
We examine the characteristics of the classical radiation emitted by a relativistic electron beam that propagates perpendicularly through a large amplitude relativistic plasma wave. Such a study is useful for evaluating the feasibility of using relativistic plasma waves as extremely short wavelength undulators for generating short wavelength radiation. The electron trajectories in a plasma wave undulator are obtained using perturbation techniques and are then compared to numerical simulation results. The frequency spectrum and angular distribution of the spontaneous radiation emitted by a single electron and the stimulated radiation gain are obtained analytically, and are then compared to 3-D numerical simulations. The characteristics of the plasma wave undulator are compared to the ac FEL undulator and the conventional FEL.
A large collisionless quiescent plasma source is developed for investigating the phase and amplitude distribution of antenna-launched whistler waves in a specified parameter regime relating wave frequency to electron cyclotron frequency. Wave dispersion is studied both by interferometer techniques with monochromatic waves and by propagation of short phase-coherent wave bursts. The wave damping mechanism is examined by propagating perfectly ducted whistler waves. The dispersion of single frequency waves and wave packets is demonstrated. Trough ducting for wave frequency to electron cyclotron frequency ratio greater than 1/2 is verified, and new eigenmodes in nonuniform plasmas at ratio values less than 1/2 are observed. It is shown that geometric effects due to ray divergence and wave refraction dominate over collisional damping.
Space weather is described as the variability of solar wind plasma that can disturb satellites and systems and affect human space exploration. Accurate prediction requires information of the heliosphere inside the orbit of the Earth. However, for predictions using remote sensing, one needs not only plane-of-sky position but also range information the third spatial dimension to show the distance to the plasma disturbances and thus when they might propagate or co-rotate to create disturbances at the orbit of the Earth. Appropriately processed radio signals from spacecraft having communications lines-of-sight passing through the inner heliosphere can be used for this spacetime localization of plasma disturbances. The solar plasma has an electron density- and radio-wavelength-dependent index of refraction. An approximately monochromatic wave propagating through a thin layer of plasma turbulence causes a geometrical-optics phase shift proportional to the electron density at the point of passage, the radio wavelength, and the thickness of the layer. This phase shift is the same for a wave propagating either up or down through the layer at the point of passage. This attribute can be used for space-time localization of plasma irregularities. The transfer function of plasma irregularities to the observed time series depends on the Doppler tracking mode. When spacecraft observations are in the two-way mode (downlink radio signal phase-locked to an uplink radio transmission), plasma fluctuations have a two-pulse response in the Doppler. In the two-way mode, the Doppler time series y2(t) is the difference between the frequency of the downlink signal received and the frequency of a ground reference oscillator. A plasma blob localized at a distance x along the line of sight perturbs the phase on both the up and down link, giving rise to two events in the two-way tracking time series separated by a time lag depending the blob s distance from the Earth: T2-2x/c, where T2 is the two-way time-of-flight of radio waves to/from the spacecraft and c is the speed of light. In some tracking situations, more information is available. For example, with the 5-link Cassini radio system, the plasma contribution to the up and down links, y(sub up)(t) and y(sub dn)(t), can be computed separately. The times series y(sub up)(t) and y(sub dn)(t) respond to a localized plasma blob with one event in each time series. These events are also separated in time by T2-2x/c. By cross-correlating the up and down link Doppler time series, the time separation of the plasma events can be measured and hence the plasma blob s distance from the Earth determined. Since the plane-of-sky position is known, this technique allows localization of plasma events in time and three space dimensions.
Electron energy loss in afterglow plasmas, plasma transport and stability and electromagnetic wave propagation through magnetoplasmas
Propagation and radiation of waves excited by electric dipole in dispersionless uniaxial moving medium
Solutions are presented for the dispersion relation of waves propagating parallel to the ambient magnetic field, in a plasma having an arbitrary ratio of thermal to magnetic pressure, beta. Previous results applicable only to wave frequencies much lower than the ion cyclotron frequency are extended to include all frequencies lower than the electron cyclotron frequency. The cyclotron turnovers are found to occur at significantly lower frequencies in finite beta plasmas. Cyclotron damping is significant for small wavelength waves. These results show that in energetic particle scattering by electromagnetic turbulence in a plasma with beta value greater than 40, scattering by waves with wave frequencies greater than the ion cyclotron frequency can be neglected. This condition is satisfied in many astrophysical plasmas.
The simulation of plasma dynamics is a critical area of Fusion Energy Sciences (FES) due to it’s usefulness in predicting, controlling, and confining plasmas in the context of potential fusion reactors. The simulation of plasmas is a computationally difficult problem in both classical and quantum physics, motivating investigation into the potential of quantum computers to simulate these systems. This project took several concrete steps towards this goal by developing tools for improving the control, characterization, and calibration of quantum gates on a superconducting quantum computer, developing error suppression and mitigation tools to reduce errors on the quantum computer, and utilizing these advancements to simulate reduced models of plasma dynamics on the quantum computer. In order to efficiently simulate plasma physics, an optimal control method which synthesizes, directly at the pulse level, any quantum gate on qubit and qutrit systems was developed. Using four superconducting transmon quantum processors at Rigetti and LLNL, it was demonstrated that any arbitrary quantum gate on qubits and qutrits could be implemented with high fidelity, leading to a significantly reduced length of a gate sequence. A problem of interest in FES is the nonlinear optical process of laser pulse compression within a plasma. Since quantum physics is linear, simulating nonlinear operations is not naturally feasible on a quantum computer, however it is possible to simulated a quantized version of the nonlinear process. A quantization approach to convert nonlinear wave-wave interaction problems to Hamiltonian simulation problems was developed and demonstrated using two qubits on a Rigetti device. In this experiment, a number of error suppression and mitigation techniques were investigated to determine how best to utilize the finite quantum resources. This study provides an example of how plasma problems may be solved on near-term, noisy quantum computing platforms and identified a promising set of techniques. Building on the insights of these experiments, the investigation turned to linear electron-plasma wave physics. A connection was identified between a local one-dimensional lattice spin model and linear wave phenomena, allowing a plasma physics problem to be efficiently mapped to the quantum computer. In this framework, reflection and transmission of plasma waves at a sharp boundary was studied, as well as the propagation of waves through an inhomogeneous plasma medium. In addition to the suite of error suppression and mitigation techniques developed, this experiment introduced the use of a digital-analog gate scheme designed to efficiently simulate the plasma Hamiltonian. With hardware available at the conclusion of the project, simulation at the scale of 9 qubits and 15 timesteps (60 entangling layers) was achieved.