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Results for “LANDAU DAMPING”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Landau damping and steepening of interplanetary nonlinear hydromagnetic waves

According to collisionless shock theories, the thickness of a shock front should be of the order of the characteristic lengths of the plasmas (the Debye length, the proton and Larmor radii, etc.). Chao and Lepping (1974), found, however, that 30% of the observed interplanetary shocks at 1 AU have thicknesses much larger than these characteristic lengths. It is the objective of the present paper to investigate whether the competition between nonlinear steepening and Landau damping can result in a wave of finite width that does not steepen into a shock. A heuristic model of such a wave is developed and tested by the examples of two structures that are qualitatively shocklike, but thicker than expected from theory. It is found that both events are in the process of steepening and their limiting thicknesses due to Landau damping are greater than the corresponding proton Larmor radius for both structures as observed at Mariner 5 (nearer the sun than 1 AU) but are comparable to the proton Larmor radius for Explorer (near 1 AU) observations.

Barnes, A.↗
DOE OSTI2022

Thermal ion kinetic effects and Landau damping in fishbone modes

We report the kinetic–magnetohydrodynamic (MHD) hybrid simulation approach for macroscopic instabilities in plasmas can be extended to include the kinetic effects of both thermal ions and energetic ions. The new coupling scheme includes synchronization of the density and parallel velocity between thermal ions and MHD, in addition to pressure coupling, to ensure the quasineutrality condition and avoid numerical errors. The new approach has been implemented in the kinetic-MHD code M3D-C1-K, and was used to study the thermal ion kinetic effects and Landau damping in fishbone modes in both DIII-D and NSTX. It is found that the thermal ion kinetic effects can cause an increase of the frequencies of the non-resonant n = 1 fishbone modes driven by energetic particles for q min >1, and Landau damping can provide additional stabilization effects. A nonlinear simulation for n = 1 fishbone mode in NSTX is also performed, and the perturbation on magnetic flux surfaces and the transport of energetic particles are calculated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Turbulent Heating in Collisionless Low-beta Plasmas: Imbalance, Landau Damping, and Electron–Ion Energy Partition

An understanding of how turbulent energy is partitioned between ions and electrons in weakly collisional plasmas is crucial for modeling many astrophysical systems. Using theory and simulations of a four-dimensional reduced model of low-beta gyrokinetics (the “Kinetic Reduced Electron Heating Model”), we investigate the dependence of collisionless heating processes on plasma beta and imbalance (normalized cross-helicity). These parameters are important because they control the helicity barrier, the formation of which divides the parameter space into two distinct regimes with remarkably different properties. In the first, at lower beta and/or imbalance, the absence of a helicity barrier allows the cascade of injected power to proceed to small (perpendicular) scales, but its slow cascade rate makes it susceptible to significant electron Landau damping, in some cases leading to a marked steepening of the magnetic spectra on scales above the ion Larmor radius. In the second, at higher beta and/or imbalance, the helicity barrier halts the cascade, confining electron Landau damping to scales above the steep “transition-range” spectral break, resulting in dominant ion heating. We formulate quantitative models of these processes that compare well to simulations in each regime, and combine them with results of previous studies to construct a simple formula for the electron–ion heating ratio as a function of beta and imbalance. This model predicts a “winner takes all” picture of low-beta plasma heating, where a small change in the fluctuations' properties at large scales (the imbalance) can cause a sudden switch between electron and ion heating.

Interplanetary turbulence↗
NASA NTRS1972

Plasma heating and acceleration due to Landau damping of hydromagnetic waves.

We analyze energy and momentum exchange associated with Landau damping of hydromagnetic waves, from a macroscopic viewpoint, and compare the conclusions with those of the resonant quasi-linear theory. It is found that the heating of protons and electrons is correctly given by the resonant theory, but that the momentum exchange is not correctly described by the resonant theory.

Barnes, A.↗
NASA NTRS1971

Nonlinear Landau damping of Alfven waves.

Demonstration that large-amplitude linearly or elliptically polarized Alfven waves propagating parallel to the average magnetic field can be dissipated by nonlinear Landau damping. The damping is due to the longitudinal electric field associated with the ion sound wave which is driven (in second order) by the Alfven wave. The damping rate can be large even in a cold plasma (beta much less than 1, but not zero), and the mechanism proposed may be the dominant one in many plasmas of astrophysical interest.

Hollweg, J. V.↗
DOE OSTI2020

ON LANDAU DAMPING RESTORATION WITH ELECTRON LENSES IN SPACE-CHARGE DOMINATED BEAMS

It is shown that the Lorentz forces of a low-energy, magnetically stabilized electron beam, or “electron lens”, can introduce transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. Unlike other nonlinear elements, the electron lens can provide the frequency spread mainly at the desirable range of particle amplitudes, thus permitting to avoid the beam lifetime degradation.

43 PARTICLE ACCELERATORS↗
NASA NTRS1980

Magnetoacoustic heating by ion Landau damping

The Vlasov-fluid model of Freidberg (1972) is used to study the resonance heating of a sharp-boundary screw pinch. The analysis provides the first treatment of the magnetoacoustic heating of a cylindrical plasma by means of ion Landau damping, which was identified as a viable dissipative mechanism for the conversion of magnetoacoustic wave energy into ion thermal energy. In addition, local and global energy conservation are considered, and formulae and numerical results for the thermal energy doubling time and the associated induced rf electric fields are presented. It is shown that collisionless absorption can provide a heating mechanism when an equilibrium plasma column is pumped by oscillations of the confining magnetic field at a frequency near the oblique magnetoacoustic frequency.

Turner, L.↗
NASA NTRS1979

Landau damping effects on solar wind fast streams

Recent measurements by the Pioneer 10 and Helios 1 spacecraft show that the leading edge of a corotating structure spreads as it moves from 0.3 AU to the orbit of the earth and steepens again farther out. By including Landau damping effects in the dynamical behavior of the streams, the above qualitative features can be accounted for.

Dangelo, N.↗
DOE OSTI2025

Surrogate Modeling of Landau Damping with Deep Operator Networks

Kinetic simulations excel at capturing microscale plasma physics phenomena with high accuracy, but their computational demands make them impractical for modeling large-scale space and astrophysical systems. In this context, we build a surrogate model, using Deep Operator Networks (DeepONets), based upon the Vlasov–Poisson simulation data to model the dynamical evolution of plasmas, focusing on the Landau damping process—a fundamental kinetic phenomenon in space and astrophysical plasmas. The trained DeepONets are able to capture the evolution of electric field energy in both linear and nonlinear regimes under various conditions. Extensive validation highlights DeepONets’ robust performance in reproducing complex plasma behaviors with high accuracy, paving the way for large-scale modeling of space and astrophysical plasmas.

plasma astrophysics↗
NASA NTRS1979

Nonlinear Landau damping in the ionosphere

A model which explains the nonresonant waves which produce the diffuse resonance observed near 3/2 f(H) by the Alouette and Isis topside sounders, where f(H) is the ambient electron cyclotron frequency, is presented. These waves are the result of plasma wave instabilities driven by anisotropic electron velocity distributions initiated by the high-power short-duration sounder pulse. Calculations of the nonlinear wave-particle coupling coefficients show that the diffuse resonance wave can be maintained by nonlinear Landau damping of the sounder-stimulated 2f(H) wave which is observed with a time duration longer than that of the diffuse resonance wave. The time duration of the diffuse resonance is determined by the transit time of the instability-generated and nonlinearly maintained diffuse resonance wave from the remote short-lived hot region back to the antenna. The model is consistent with the Alouette/Isis observations and it demonstrates the existence of nonlinear wave-particle interactions in the ionosphere.

Kiwamoto, Y.↗
NASA NTRS1972

Resonance, particle trapping, and Landau damping in finite amplitude obliquely propagating waves

The equations of motion for a particle in resonance with a small finite amplitude wave are solved approximately, using secularity free perturbation theory. The wave propagates at an arbitrary angle to a uniform background magnetic field in an infinite collisionless plasma. The wave fields include a longitudinal electrostatic component and elliptically polarized transverse electric and magnetic components. The trajectories of trapped and resonant untrapped particles are described, for each of the possible wave-particle resonances. These trajectories are used to construct an estimate of the nonlinear time dependent Landau damping rate of the wave.

Palmadesso, P. J.↗
NASA NTRS1994

Landau damping of magnetospherically reflected whistlers

Unducted VLF signals produced by lightning activity can form a population of magnetospherically reflected (MR) whistlers in the inner magnetosphere. It has been suggested recently that in the absence of significant attenuation such waves could merge into a broadband continuum with sufficient intensity to account for plasmaspheric hiss. To test this conjecture we have evaluated the path-integrated attenuation of MR whistlers along representative ray paths using the HOTRAY code. Using a realistic plasma distribution modeled on in-situ data, we find that the majority of MR waves experience significant damping after a few transits across the equator. This is primarily due to Landau resonance with suprathermal (0.1-1 keV) electrons. The attenuation is most pronounced for waves that propagate through the outer plasmasphere; this can readily account for the infrequent occurrence of multiple-hop MR waves for L greater than or equal to 3.5. Selected waves that originate at intermediate latitudes (15 deg is less than or equal to lambda is less than or equal to 35 deg) and whose ray paths are confined to the inner plasma- sphere may experience up to 10 magnetospheric reflections before substantial attentuation occurs. These waves should form the population of observed MR waves. Wave attenuation becomes more pronounced at higher frequencies; this can account for the absence of multiple-hop waves above 5 kHz. Weakly attenuated MR waves tend to migrate outward to the L shell, where their frequency is comparable to the equatorial lower hybrid frequency. The enhanced concentration of waves due to a merging of ray paths would produce a spectral feature that rises in frequency at lower L. This is quite distinct from the reported properties of plasmaspheric hiss, which maintains a constant frequency band throughout the entire plasmasphere. Furthermore, in the absence of mode conversion, waves below 500 Hz, which often form an important if not dominant part of the spectral properties of hiss, are unable to escape from the topside ionosphere in the whistler mode. Consequently, we conclude that unducted lightning signals cannot account for the origin of plasmaspheric hiss.

Thorne, Richard M.↗