Search NASA⌕ Search

SEARCH · Search NASA

Results for “WHISTLER”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Influence of plasma beta on the generation of lower hybrid and whistler waves by an ion velocity ring distribution

We present results of three-dimensional electromagnetic particle-in-cell simulations of the lower hybrid ion ring instability, similar to our earlier results [D. Winske and W. Daughton, Phys. Plasma 19, 072109 (2012)], but at higher electron beta (β{sub e} = ratio of electron thermal pressure to magnetic pressure = 0.06, rather than at 0.006) with T{sub i} = T{sub e}. At higher electron beta, the level of lower hybrid waves at saturation normalized to the ion thermal energy (β{sub i} = 0.06 also) is only slightly smaller, but the corresponding magnetic fluctuations are about an order of magnitude larger, consistent with linear theory. After saturation, the waves evolve into whistler waves, through a number of possible mechanisms, with an average growth rate considerably smaller than the linear growth rate of the lower hybrid waves, to a peak fluctuation level that is about 20% above the lower hybrid wave saturation level. The ratio of the peak magnetic fluctuations associated with the whistler waves relative to those of the saturated lower hybrid waves, the ratio of the nonlinear growth rate of whistlers relative to the linear growth rate of lower hybrid waves, the amount of energy extracted from the ring, and the amount of heating of the background ions and electrons are comparable to those in the lower electron beta 3D simulation. This suggests that even at higher electron beta, the linear and nonlinear physics of the lower hybrid ion ring instability is dominated by electrostatic, wave-particle rather than wave-wave interactions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1976

Deuteron whistler and trans-equatorial propagation of the ion cyclotron whistler

The paper investigates two unusual types of ion cyclotron whistlers that were found in the low-latitude topside ionosphere by analyzing ISIS VLF electric-field data received at Kashima, Japan. One type is characterized by an asymptotic frequency equal to one half the local proton gyrofrequency; the asymptotic frequency of the other type corresponds to the minimum proton gyrofrequency along the geomagnetic field line passing through the satellite. The observations are compared with theoretical spectrograms of the ion cyclotron whistlers computed for appropriate model distributions of electrons and ions in the topside ionosphere. It is found that the whistlers with the asymptotic frequency of one half the local proton gyrofrequency are deuteron whistlers and that the other whistlers are due to the transequatorial propagation of proton or deuteron whistlers originating in the southern hemisphere.

Watanabe, S.↗
DOE OSTI2016

Whistler turbulence heating of electrons and ions: Three-dimensional particle-in-cell simuations

In this study, the decay of whistler turbulence in a collisionless, homogeneous, magnetized plasma is studied using three-dimensional particle-in-cell simulations. The simulations are initialized with a narrowband, relatively isotropic distribution of long wavelength whistler modes. A first ensemble of simulations at electron beta ${\beta }_{{\rm{e}}}$ = 0.25 and ion-to-electron mass ratio ${m}_{{\rm{i}}}$/${m}_{{\rm{e}}}$ = 400 is carried out on a domain cube of dimension $L{\omega }_{\mathrm{pi}}$/c = 5.12 where ${\omega }_{\mathrm{pi}}$ is the ion plasma frequency. The simulations begin with a range of dimensionless fluctuating field energy densities, ${\epsilon }_{{\rm{o}}}$, and follow the fluctuations as they cascade to broadband, anisotropic turbulence which dissipates at shorter wavelengths, heating both electrons and ions. The electron heating is stronger and preferentially parallel/antiparallel to the background magnetic field ${{\boldsymbol{B}}}_{{\rm{o}}};$ the ion energy gain is weaker and is preferentially in directions perpendicular to ${{\boldsymbol{B}}}_{{\rm{o}}}$. The important new results here are that, over 0.01 < ${\epsilon }_{{\rm{o}}}$ < 0.25, the maximum rate of electron heating scales approximately as ${\epsilon }_{{\rm{o}}}$, and the maximum rate of ion heating scales approximately as ${\epsilon }_{{\rm{o}}}^{1.5}$. A second ensemble of simulations at ${\epsilon }_{{\rm{o}}}$ = 0.10 and ${\beta }_{{\rm{e}}}$ = 0.25 shows that, over 25 < ${m}_{{\rm{i}}}$/${m}_{{\rm{e}}}\;$< 1836, the ratio of the maximum ion heating rate to the maximum electron heating rate scales approximately as ${m}_{{\rm{e}}}$/${m}_{{\rm{i}}}$.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

WHISTLER TURBULENCE FORWARD CASCADE VERSUS INVERSE CASCADE: THREE-DIMENSIONAL PARTICLE-IN-CELL SIMULATIONS

We present the results of the first fully three-dimensional particle-in-cell simulations of decaying whistler turbulence in a magnetized, homogeneous, collisionless plasma in which both forward cascades to shorter wavelengths, and inverse cascades to longer wavelengths are allowed to proceed. For the electron beta β {sub e} = 0.10 initial value considered here, the early-time rate of inverse cascade is very much smaller than the rate of forward cascade, so that at late times the fluctuation energy in the regime of the inverse cascade is much weaker than that in the forward cascade regime. Similarly, the wavevector anisotropy in the inverse cascade regime is much weaker than that in the forward cascade regime.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Extreme ultra-violet burst, particle heating, and whistler wave emission in fast magnetic reconnection induced by kink-driven Rayleigh-Taylor instability

A spatially localized energetic extreme ultra-violet (EUV) burst is imaged at the presumed position of fast magnetic reconnection in a plasma jet produced by a coaxial helicity injection source; this EUV burst indicates strong localized electron heating. A circularly polarized high frequency magnetic field perturbation is simultaneously observed at some distance from the reconnection region indicating that the reconnection emits whistler waves and that Hall dynamics likely governs the reconnection. Spectroscopic measurement also shows simultaneous fast ion heating. The electron heating is consistent with Ohmic dissipation, while the ion heating is consistent with ion trajectories becoming stochastic.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

On the parameter dependence of the whistler anisotropy instability

The evolution of the whistler anisotropy instability relevant to whistler-mode chorus waves in the Earth’s inner magnetosphere is studied using kinetic simulations and is compared with satellite observations. The electron distribution is constrained by the whistler anisotropy instability to a marginal stability state and presents an upper bound of electron anisotropy, which agrees with satellite observations. The electron beta β ∥e separates whistler waves into two groups: (i) quasi-parallel whistler waves for β ∥e ≳ 0.02 and (ii) oblique whistler waves close to the resonance cone for β ∥e ≲ 0.02. Landau damping is important in the saturation and relaxation stage of the oblique whistler wave growth. The saturated magnetic field energy of whistler waves roughly scales with the electron beta β 2 ∥e , shown in both simulations and satellite observations. Lastly, these results suggest the critical role of electron beta β ∥e in determining the whistler wave properties in the inner magnetosphere.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1995

Propagation and damping of broadband upstream whistlers

Previous studies indicated that damping rates of upstream whistlers strongly depend on the details of the electron distribution function. Moreover, detailed analysis of Doppler-shift and whistler dispersion relation indicated that upstream whistlers propagate obliquely in a broad band. In this paper we present results of a kinetic calculation of damping lengths of wide-band whistlers using the sum of 7-drifting bi-Maxwellian electron distributions as a best fit to the International Sun Earth Explorer (ISEE) 1 electron data. For 2 cases, when upstream whistlers are observed, convective damping lengths derived from ISEE magnetic field and ephemeris data are compared with theoretical results. We find that the calculated convective damping lengths are consistent with the data and that upstream whistlers remain marginally stable. We also show that the slope of plasma frame spectra of upstream whistlers, obtained by direct fitting of the observed spectra is between 5 and 7 with a sharp lower frequency cutoff corresponding to a wavelength of about one ion inertial length. When the solar wind velocity is directed largely along the wave normal of the upstream whistlers the polariztion of the right hand waves becomes reversed and low frequencies are switched to high resulting in a peaked spectrum with a strong high frequency cutoff. The overall spectral, wave and particle characteristics, proximity to the shock as well as propagation and damping properties indicate that these waves cannot be generated locally. Instead the observed upstream whistlers arise in the shock ramp most likely by a variety of cross-field drift and/or anisotropy driven instabilities.

Orlowski, D. S.↗
NASA NTRS1985

A summary of whistlers observed by Voyager 1 at Jupiter

We summarize the Voyager 1 observations of whistlers at Jupiter in order to provide a basis for further analyses of the density profile of the Io plasma torus as well as to support studies of atmospheric lightning at Jupiter. All the whistlers detected by Voyager 1 fell into three general regions in the torus at radial distances ranging beteen 5 and 6 R sub J. An analysis of the broadband wave amplitudes measured by the Voyayer 1 plasma wave instrument and estimates of the peak whistler amplitudes imply the grouping of whistlers was due to variations in the sensitivity of the receiver to whistlers and not to variations in the source or propagation paths of the whistlers. The whistler dispersions are presented in statistical form for each of the three groups of events and analyzed in view of the structure of the Io plasma torus as determined by plasma probe measurements. The results of these analyses give source locations for the whistlers at the foot of the magnetic field lines threading the torus in both hemispheres and over a range of longitudes.

Kurth, W. S.↗
NASA NTRS1994

New aspects of whistler waves driven by an electron beam studied by a 3-D electromagnetic code

We have restudied electron beam driven whistler waves with a 3-D electromagnetic particle code. The simulation results show electromagnetic whistler wave emissions and electrostatic beam modes like those observed in the Spacelab 2 electron beam experiment. It has been suggested in the past that the spatial bunching of beam electrons associated with the beam mode may directly generate whistler waves. However, the simulation results indicate several inconsistencies with this picture: (1) whistler waves continue to be generated even after the beam mode space charge modulation looses its coherence, (2) the parallel (to the background magnetic field) wavelength of the whistler wave is longer than that of the beam instability, and (3) the parallel phase velocity of the whistler wave is smaller than that of the beam mode. The complex structure of the whistler waves in the vicinity of the beam suggest that the transverse motion (gyration) of the beam and background electrons is also involved in the generation of whistler waves.

Nishikawa, Ken-Ichi↗
NASA NTRS2011

Large Amplitude Whistlers in the Magnetosphere Observed with Wind-Waves

We describe the results of a statistical survey of Wind-Waves data motivated by the recent STEREO/Waves discovery of large-amplitude whistlers in the inner magnetosphere. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 h inside 5 R(sub E) and 431 h inside 10 R(sub E) during the 8 years (1994-2002) that it orbited the Earth. Five episodes were found when whistlers had amplitudes comparable to those of Cattell et al. (2008), i.e., electric fields of 100 m V/m or greater. The whistlers usually occurred near the plasmapause. The observations are generally consistent with the whistlers observed by STEREO. In contrast with STEREO, Wind-Waves had a search coil, so magnetic measurements are available, enabling determination of the wave vector without a model. Eleven whistler events with useable magnetic measurements were found. The wave vectors of these are distributed around the magnetic field direction with angles from 4 to 48deg. Approximations to observed electron distribution functions show a Kennel-Petschek instability which, however, does not seem to produce the observed whistlers. One Wind episode was sampled at 120,000 samples/s, and these events showed a signature that is interpreted as trapping of electrons in the electrostatic potential of an oblique whistler. Similar waveforms are found in the STEREO data. In addition to the whistler waves, large amplitude, short duration solitary waves (up to 100 mV/m), presumed to be electron holes, occur in these passes, primarily on plasma sheet field lines mapping to the auroral zone.

Kellogg, P. J.↗
NASA NTRS2019

Source of the Bursty Bulk Flow Diffuse Aurora: Electrostatic Cyclotron Harmonic and Whistler Waves in the Coupling of Bursty Bulk Flows to Auroral Precipitation

Electron cyclotron harmonic (ECH) and whistler chorus waves are recognized as the two mechanisms responsible for the resonant wave‐particle interactions necessary to precipitate plasma sheet electrons into the ionosphere, producing the diffuse Aurora. Previous work has demonstrated ECH waves dominate electron scattering at L shells >8, while whistler chorus dominates scattering at L shells L < 8. However, we find from Time History of Events and Macroscale (THEMIS) Interactions during Substorms observations of fast flows at L = 12 that oblique whistler chorus emissions play the dominant role in scattering electrons. Previous works have identified whistler‐mode waves within fast flows that are produced by an electron temperature anisotropy Te,⊥/Te,||> 1, consistent with electron betatron acceleration. Here, however, we find whistler chorus emissions throughout an interval of fast flows where Te,⊥/Te,||< 1. Parallel electron beams account for the enhanced parallel electron temperature and serve as the instability mechanism for the whistler chorus. The parallel electron beams and associated cigar‐shaped distributions are consistent with Fermi acceleration at dipolarizations in fast flows. We demonstrate that the scattering efficiency of the whistler chorus exceeds that of ECH waves, which THEMIS also detects during the fast flows. The obliquity of the whistler waves permits efficient scattering of lower‐energy electrons into the diffuse aurora. We conclude that Fermi acceleration of electrons provides one important free‐energy source for the wave‐particle interactions responsible for coupling plasma sheet electrons into the diffuse aurora during substorm conditions.

Wendel, D. E.↗
DOE OSTI2014

Whistler mode waves and the electron heat flux in the solar wind: cluster observations

The nature of the magnetic field fluctuations in the solar wind between the ion and electron scales is still under debate. Using the Cluster/STAFF instrument, we make a survey of the power spectral density and of the polarization of these fluctuations at frequencies f in [1, 400] Hz, during five years (2001-2005), when Cluster was in the free solar wind. In ∼10% of the selected data, we observe narrowband, right-handed, circularly polarized fluctuations, with wave vectors quasi-parallel to the mean magnetic field, superimposed on the spectrum of the permanent background turbulence. We interpret these coherent fluctuations as whistler mode waves. The lifetime of these waves varies between a few seconds and several hours. Here, we present, for the first time, an analysis of long-lived whistler waves, i.e., lasting more than five minutes. We find several necessary (but not sufficient) conditions for the observation of whistler waves, mainly a low level of background turbulence, a slow wind, a relatively large electron heat flux, and a low electron collision frequency. When the electron parallel beta factor β {sub e∥} is larger than 3, the whistler waves are seen along the heat flux threshold of the whistler heat flux instability. The presence of such whistler waves confirms that the whistler heat flux instability contributes to the regulation of the solar wind heat flux, at least for β {sub e∥} ≥ 3, in slow wind at 1 AU.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Nonlinear Electrostatic Steepening of Whistler Waves: The Guiding Factors and Dynamics in Inhomogeneous Systems

Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The efficiency of wave-particle resonant interactions is defined by whistler wave properties which have been described by the approximation of plane linear waves propagating through the cold plasma of the inner magnetosphere. However, recent observations of extremely high-amplitude whistlers suggest the importance of nonlinear wave-particle interactions for the dynamics of the outer radiation belt. Oblique chorus waves observed in the inner magnetosphere often exhibit drastically nonsinusoidal (with significant power in the higher harmonics) waveforms of the parallel electric field, presumably due to the feedback from hot resonant electrons. We have considered the nature and properties of such nonlinear whistler waves observed by the Van Allen Probes and Time History of Events and Macroscale Interactions define during Substorms in the inner magnetosphere, and we show that the significant enhancement of the wave electrostatic component can result from whistler wave coupling with the beam-driven electrostatic mode through the resonant interaction with hot electron beams. Being modulated by a whistler wave, the electron beam generates a driven electrostatic mode significantly enhancing the parallel electric field of the initial whistler wave. Finally, we confirm this mechanism using a self-consistent particle-in-cell simulation. The nonlinear electrostatic component manifests properties of the beam-driven electron acoustic mode and can be responsible for effective electron acceleration in the inhomogeneous magnetic field.

58 GEOSCIENCES↗
DOE OSTI2019

Whistler wave generation by electron temperature anisotropy during magnetic reconnection at the magnetopause

Two magnetopause reconnection events of the Magnetospheric Multiscale mission with whistler wave activity are presented. The whistler mode around half of the electron cyclotron frequency is excited near the magnetospheric separatrix. In both events, there are positive correlations between the whistler wave and the lower hybrid drift instability (LHDI) activities, suggesting a possible role of LHDI in the whistler wave generation. A sudden change in the electron pitch angle distribution (PAD) function of energetic electrons is observed right after intense LHDI activity. This change in the PAD leads to temperature anisotropy in energetic electrons which is responsible for the whistler wave excitation. The measured dispersion relation demonstrates that the whistler wave propagates toward the X line nearly parallel to the magnetic field line. Furthermore, a linear analysis with the measured distribution function verifies that the whistler mode is excited by the temperature anisotropy in energetic electrons.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1976

Magnetospheric whistler ducts observed by ISIS satellites

The latitudinal width of the magnetospheric whistler duct has been estimated by the first and final invariant latitudes of whistler echoes and the conservation of the magnetic flux for the centered dipole field, using 105 whistler echoes in ISIS VLF data received at Kashima, Japan for 1972-1973. The latitudinal distribution of whistler duct occurrence shows a maximum at invariant latitudes of 40-45 degrees near the maximum occurrence latitude of ground whistlers. The radial width of magnetospheric whistler duct in the geomagnetically equatorial plane increases with invariant latitude of the geomagnetic flux tube in which whistlers propagate.

Ondoh, T.↗
NASA NTRS1981

A comparison of equatorial electron densities measured by whistlers and by a satellite radio technique

Magnetospheric equatorial electron densities determined from whistler observations are compared with in situ satellite measurements of electron density along near-equatorial orbits. Whistler data was recorded at Siple and Palmer, Antarctica, while the sweep frequency receiver on ISEE-1 was used to measure plasma densities during passes within about 15 deg of the whistler station longitudes at L values between 3 and 5.2. The whistler and satellite data sets are found to be in good agreement for the three rendezvous considered, suggesting that the diffusive equilibrium model applied to calculate electron densities from whistler measurements was appropriate for the description of electron density distributions along field lines in the outer plasmasphere. Data also indicate that density enhancements within the whistler ducts were not more than about 30% of the mean or interduct level, and that there were no significant east-west density gradients within about 15 deg of whistler station longitudes over the L range of the study.

Carpenter, D. L.↗
NASA NTRS1993

Whistlers and plasmaspheric hiss - Wave directions and three-dimensional propagation

Wave propagation directions are determined on the basis of wave data from the DE 1 satellite showing simultaneously nonducted whistlers and hiss. Hiss wave normal angles are determined as about 70 and 77 deg for f = 3.5 and 2.5 kHz, respectively, with the wave vector being almost perpendicular to the meridional plane. A novel approximate analytical formulation of 3D propagation of whistler waves is developed and used to model the drift of magnetospherically reflected whistlers in azimuth. It is shown that depending on initial parameters, the time of arrival of whistler rays at a fixed observation point can differ by 10-20 s, with signals from different magnetospherically reflected whistlers overlapping to evolve into a hisslike signal. The total azimuthal drift of whistler rays is found to not exceed about 30 deg, so that plasmaspheric hiss may be produced by nonducted whistlers at longitudes correlated with the location of thunderstorm activity.

Draganov, A. B.↗
DOE OSTI2025

Excitation of whistler and slow-X waves by runaway electrons in a collisional plasma

Runaway electrons are known to provide robust ideal or collisionless kinetic drive for plasma wave instabilities in both the whistler and slow-X branches, via the anomalous Doppler-shifted cyclotron resonances. In a cold and dense post-thermal-quench plasma, collisional damping of the plasma waves can compete with the collisionless drive. Previous studies have found that, due to their higher wavelength and frequency, slow-X waves suffer stronger collisional damping than the whistlers, while the ideal growth rate of slow-X modes is higher. Here, we study runaway avalanche distributions that maintain the same eigen distribution and increase only in magnitude over time. The distributions are computed from the relativistic Fokker–Planck–Boltzmann solver, upon which a linear dispersion analysis is performed to search for the most unstable or least damped slow-X and whistler modes. Taking into account the effect of plasma density, plasma temperature, and effective charge number, we find that the slow-X modes tend to be excited before the whistlers in a runaway current ramp-up. Furthermore, even when the runaway current density is sufficiently high that both branches are excited, the most unstable slow-X mode has a much higher growth rate than the most unstable whistler mode. The qualitative and quantitative trends uncovered in the current study indicate that even though past experiments and modeling efforts have concentrated on whistler modes, there is a compelling case that slow-X modes should also be a key area of focus in the runaway self-mediation through wave instabilities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗