Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “electron cyclotron emission”

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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

The magnetoionic modes and propagation properties of auroral radio emissions

The nature of the magnetoionic wave modes which accompany the aurora is clarified here by a detailed analysis, using multiple techniques, of DE 1 auroral radio observations. All four of the possible magnetoionic wave modes are found to occur, apparently emitted from two different source regions on the same auroral field line. AKR originates primarily in the X mode near the electron cyclotron frequency, and is frequently also accompanied by a weaker O-mode component from the same location. The next most prominent auroral emission is the W-mode auroral hiss originating from altitudes always well below the DE 1 satellite at frequencies below the local cyclotron frequency. The previously reported Z-mode auroral radiation was also detected, but from sources also below the satellite at the poleward edge of the cavity, and not from the expected AKR source at the cyclotron frequency.

Calvert, Wynne↗
NASA NTRS1983

Plasma waves in planetary magnetospheres

Research conducted within the last four years on plasma waves in the terrestrial magnetosphere as well as those of Jupiter and Saturn is reviewed. Studies aimed at the characterization of plasma wave emissions in the earth's magnetosheath and magnetopause are considered, together with investigations of the characteristics and mechanisms of electron cyclotron harmonic and upper hybrid resonance waves, nonthermal continuum radiation, auroral kilometric radiation, chorus, hiss and whistler-mode turbulence, whistlers, power line radiation, ion cyclotron waves, an ionospheric irregularities and instabilities. Experimental studies based on the injection of waves or plasma into the ionosphere and plasma waves in the laboratory are also examined. In situ Voyager data and radio astronomical observations of Jupiter are discussed as they relate to the plasma waves detected in the Jovian mgnetosheath and magnetopause, outer and inner magnetosphere and magnetotail, as well as the Jovian radio emission. In the case of Saturn, particular attention is given to the emissions observed during the Voyager encounter with the planet, its rings and Titan.

Anderson, R. R.↗
DOE OSTI2023

Observation of impurity accumulation and its compatibility with high plasma performance in W7-X

At the W7-X stellarator, the bolometer system has measured an intensive radiation zone in the inner plasma region (at a normalized radius $ρ$ ~ 0.3–0.4) in the hydrogen plasma generated by electron cyclotron resonance heating; it differs from the normal plasma radiation distribution with an edge-localized emission zone. Spectroscopic diagnostics have recorded high-Z elements such as iron. This phenomenon happens in the plasma phases after gas supply turn-off, which results in all impurity relevant diagnostic signals increasing for several seconds. Despite the enhancement of the core radiation, the plasma energy confinement is improved. A transport analysis shows that this impurity radiation behavior is associated with a low diffusion coefficient ($D$~ 0.02 m 2 s -1 ) and a reversal of the convection around the radial position of the emission peak, which, under normal conditions, separates the zones of outward convection in the central (|$V$| ~ 0.1 m s -1 ) and inward convection in the outer region (|$V$| ~ 0.3 m s -1 ). An impurity accumulation around this radial position has been identified. The transport coefficients obtained are comparable with the theoretical predictions of collisional impurity transport. In the plasma phases studied, both impurity and energy confinement are enhanced. The mechanism responsible for the improvement is believed to be a reduction of micro-instabilities associated with the observed steepening of the density profile, initiated by a low edge plasma density (<1.0 × 10 19 m -3 ) after switching off the gas fueling. The normalized temperature and density gradients fulfil the condition for the suppression of ITG turbulence.

suppression of ITG turbulence↗
DOE OSTI2023

Developing a Cyclotron Radiation Emission Spectroscopy Detection System

Cyclotron Radiation Emission Spectroscopy is a new technique for ultra-precise spectroscopy of low-energy electrons. This project aimed at developing capabilities that would be useful to a future CRES experiment. The recent results from the Project 8 and He6-CRES collaborations indicate that CRES has a promising future, but will need advancements to continue developing. In this report we cover the four tasks that comprised the project: data acquisition, data management, updating the raw-data format, a cloud computing.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Monte Carlo Simulations of Polarized Radiative Transfer in Neutron Star Atmospheres

Soft X-ray emission from neutron stars affords powerful diagnostic tools for uncovering their surface and interior properties, as well as their geometric configurations. In the atmospheres of neutron stars, the presence of magnetic fields alters the photon-electron scattering cross sections, resulting in nontrivial angular dependence of intensity and polarization of the emergent signals. This paper presents recent developments of our Monte Carlo simulation, MAGTHOMSCATT, which tracks the complex electric field vector for each photon during its transport. Our analysis encompasses the anisotropy and polarization characteristics of X-ray emission for field strengths ranging from nonmagnetic to extremely magnetized regimes that are germane to magnetars. In the very low field domain, we reproduced the numerical solution to the radiative transfer equation for nonmagnetic Thomson scattering, and provided analytical fits for the angular dependence of the intensity and the polarization degree. These fits can be useful for studies of millisecond pulsars and magnetic white dwarfs. By implementing a refined injection protocol, we show that, in the magnetar regime, the simulated intensity and polarization pulse profiles of emission from extended surface regions becomes invariant with respect to the ratio of photon (ω) and electron cyclotron (ω B ) frequencies once ω/ω B ≲ 0.01. This circumvents the need for simulations pertinent to really high magnetic field strengths, which are inherently slower. Our approach will be employed elsewhere to model observational data to constrain neutron star geometric parameters and properties of emitting hot spots on their surfaces.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1982

Transient effects in beam-plasma interactions in a space simulation chamber stimulated by a fast pulse electron gun

Interest in the interaction of electron beams with plasma generated by ionization caused by the primary electron beam was stimulated by the need to develop special vacuum tubes to operate in the kMHz frequency region. The experiments of Getty and Smullin (1963) indicated that the interaction of an energetic electron beam with its self-produced plasma resulted in the emission of wave energy over a wide range of frequencies associated with cyclotron and longitudinal plasma instabilities. This enhanced the thermal plasma density in the vicinity of the beam, and the term Beam-Plasma Discharge (BPD) was employed to described this phenomenon. The present investigation is concerned with some of the transient phenomena associated with wave emission during the beam switch-on and switch-off periods. Results are presented on the changes in electron energy spectra on a time scale of tens of milliseconds following beam switch-on. The results are discussed in terms of the beam plasma discharge phenomenon.

Raitt, W. J.↗
NASA NTRS1995

Emission of Whistler-mode waves and diffusion of electrons around interplanetary shocks

Whistler-mode wave emissions are frequently observed at and downstream of interplanetary shocks. Using electron distribution functions measured onboard Ulysses in the energy range 1.6 to 862 eV, we calculate the temperature anisotropy and the wave growth rate of the electromagnetic electron cyclotron instability, Results of the calculations are compared to the whistler wave spectra observed simultaneously. For the studied events there is a good correlation between the wave growth rates and the wave spectra. Particularly, upstream of the shock front where no wave emissions are observed, the anisotropy lies below the wave instability threshold, i.e. the critical anisotropy Ac; on the contrary, downstream of the shock, the anisotropy exceeds Ac in some frequency range. Moreover. the tact that the anisotropy is close to Ac in a large frequency range gives prominence to the effect of velocity space diffusion of the electrons by the waves.

Pierre, F.↗
NASA NTRS1995

Coincident bursts of auroral kilometric radiation and VLF emissions associted with a type 3 solar radio noise event

This paper examines an isolated magnetospheric VLF/radio noise event that is highly suggestive of the triggering of terrestrial auroral kilometric radiation (AKR) bu solar type III radio emission and of a close relation between AKR and broadband hiss. The solar type III burst was measured on polar HF riometers and was coincident with local dayside VLF/LF noise emission bursts at South Pole station. It was also coincident with AKR bursts detected onthe AMPTE/IRM satellite, at the same magnetic local time as South Pole. On the basis of the close association of AKR and VLF bursts, and from geometric considerations relating to wave propagation, it is likely that the AKR source was on the dayside and on field lines near South Pole station. The general level of geomagnetic activity was very low. However, an isolated magnetic impulse event (MIE) accompanied by a riometer absorption pulse was in progress when all of the VLF/radio noise bursts occurred. The very close association of the typew III burst at HF with the AKR is consistent with external stimulation of the AKR, is different, more immediate,triggering process than that implied by Calvert (1981) is invoked. It is suggested here that some of the HF solar radiant energy may decay into waves with frequences comparable to those of the AKR by paraetric excitation or some other process, thus providing the few background photons required for the generation of AKR by the WU and Lee (1979) cyclotron maser instability. The AKR, perhaps by modifying the magnetospheric electron velocity distribution, might have produced the observed VLF emissions. Alternatively, the VLF emissions may have arisen from the same anisotropic and unstable electron distribution function responsible for the AKR.

Rosenberg, T. J.↗
NASA NTRS1984

Electron-cyclotron maser radiation from a relativistic loss-cone distribution

A relativistic analysis of the electron-cyclotron maser instability in a loss-cone distribution is presented, extending the treatment of Lau and Chu (1983) to include the effects of finite k-perpendicular (as encountered in laboratory tandem-mirror devices with mean energies in excess of 50 keV). The results are presented in graphs, and it is found that the k-perpendicular effects are significant, so that emission perpendicular to the magnetic field is associated with most rapid growth of the instability. The persistence of the instability when the ratio of the plasma frequency to the electron-cyclotron frequency is less than 0.1 is demonstrated, and the factors which need to be accounted for in applying the results to actual mirror devices are indicated.

Pritchett, P. L.↗
NASA NTRS1978

Plasma waves near the sun: Advances possible with a solar probe

A review is presented of current experimental and theoretical knowledge of plasma waves in the solar wind, with comments on the scientific importance of obtaining plasma wave measurements in the region near the sun with the solar probe. The waves discussed include the acoustic waves and shocks which are thought to be the primary source for heating the solar corona, Alfven waves, ion-cyclotron waves, whistler-mode turbulence, ion-acoustic waves, and electron plasma oscillations associated with solar radio emissions. A discussion is presented of the types of measurements which would be needed to study these waves on the solar probe, the constraints imposed on the spacecraft and the research and development which would be needed to provide the necessary instrumentation.

Gurnett, D. A.↗
NASA NTRS1989

Comptonization of thermal photons by relativistic electron beams

This paper presents a numerical calculation of gamma-ray emission produced by Compton scattering of relativistic electron beams on background thermal radiation, which includes spatial dependence of electron energy losses and cyclotron resonance scattering in a strong magnetic field. In the first version, the scattering is described by the fully relativistic Klein-Nishina cross section, but the magnetic field is neglected. In the second version, the scattering is described by the magnetic resonant cross section in the Thomson limit. It is found that when the magnetic field is not included, electron energy losses are important only at higher neutron star surface temperatures (T about 3,000,000 K). In the presence of a strong magnetic field, (10 to the 12th G), resonant scattering greatly increases electron energy losses, making scattering very efficient even at lower surface temperatures. Resulting photon and electron spectra for both cases ae discussed in relation to models for pulsar X-ray and gamma-ray emission.

Daugherty, Joseph K.↗
NASA NTRS1983

Accretion powered X-ray pulsars

The current theoretical understanding of the properties of X-ray pulsars is assessed through a comparison with unified descriptions of 14 such systems, extending over six orders of magnitude in luminosity, in whose phase averaged spectra the only notable trend is a less abrupt high energy cutoff in the lower luminosity systems. Detailed pulse phase spectroscopy is given for five of the systems. A reexamination of the pulse phase spectra of 4U 0115 + 63 has uncovered electron cyclotron lines at 11.5 and 23 keV that appear to be in absorption at pulse peak and in emission during an interpulse. Spectral hardening regions such as those from Her X-1 are a common feature in the low energy pulse of many pulsars, and may represent the passage of the magnetic axis through the observer's line of sight. Attention is given to the nature of the beaming from Her X-1, and it is concluded that a pencil beam configuration represents the simplest explanation of the overall properties of the pulse.

White, N. E.↗
NASA NTRS1984

A simulation study of the loss cone driven cyclotron maser applied to auroral kilometric radiation

The linear growth and nonlinear saturation of electromagnetic radiation amplified by a hot (5-20 keV) population of electrons possessing a loss cone velocity distribution in the presence of a cold (20-500 eV) electron population are studied. A relativistic electromagnetic simulation code is used to study the emission process. Three cases are presented in detail to illustrate the generation process of auroral kilometric radiation. The first case, which has an electron plasma frequency omega(pe) = 0.2 omega(ce) (electron cyclotron frequency) and possesses a double loss cone distribution, exhibits a strong narrow peak of the fast extraordinary mode (X mode) radiation just above the X mode cutoff frequency. The second case with omega(pe) = 0.2 omega(ce) and a single loss cone distribution shows a preferred direction of propagation for the amplified radiation. The third case with omega(pe) = 0.5 omega(ce) shows a peak in the ordinary mode (O mode) radiation. In all cases, the radiation saturates by turbulent scattering of resonant particles into the loss cone.

Wagner, J. S.↗
NASA NTRS2006

Is the Linear Mode Conversion Theory Viable for Generating Kilometric Continuum?

Kilometric Continuum (KC) usually exhibits a complicated banded radiation pattern observed in frequency time spectrograms. Can the number of bands, the frequency range over which the bands are observed, and their time variation be explained with Linear Mode Conversion Theory (LMCT) using realistic plasmapause models and Extreme Ultraviolet (EUV) plasmaspheric observations? In this paper we compare KC observations with simulated frequency emission bands based on LMCT for a number of cases. In LMCT the allowed frequency range across the equatorial plasmapause is restricted to frequencies much greater than the electron cyclotron frequency (fce) and less than the maximum plasma frequency in this region. Fce also determines the number of allowed bands in this range. Is the observed frequency range and number of bands consistent with the predications of LMCT? Can irregularities in the shape of plasmaspheric structures like notches be observed in the time variations of KC emissions? We will investigate these and other questions. Simulated radiation patterns will be generated by ray tracing calculations in the L-O mode from the radio window at the near equatorial plasmapause. The KC observations used in this study are from the Plasma Wave Instrument on the Geotail spacecraft and from the Radio Plasma Imager on the IMAGE spacecraft. The plasmasphere and plasmapause will be derived either from plasmasphere simulations, from images by the EUV imager on the IMAGE spacecraft, and by using empirical models. In situ plasma density measurements from a number of spacecraft will also be used in order to reconstruct the plasmasphere for these case studies.

Boardsen, Scott A.↗
NASA NTRS1986

RF wave observations in beam-plasma discharge

The Beam Plasma Discharge (BPD) was produced in the large vacuum chamber at Johnson Space Center (20 x 30 m) using an energetic electron beam of moderately high perveance. A more complete expression of the threshold current I sub c taking into account the pitch angle injection dependence is given. Ambient plasma density inferred from wave measurements under various beam conditions are reported. Maximum frequency of the excited RF band behaves differently than the frequency of the peak amplitude. The latter shows signs of parabolic saturation consistent with the light data. Beam plasma state (pre-BPD or BPD) does not affect the pitch angle dependence. Unexpected strong modulation of the RF spectrum at half odd integer of the electron cyclotron frequency (n + 1/2)f sub ce is reported (5 n 10). Another new feature, the presence of wave emission around 3/2 f sub ce for I sub b is approximate I sub c is reported.

Bernstein, W.↗
NASA NTRS1987

Evolution of the axial electron cyclotron maser instability, with applications to solar microwave spikes

The nonlinear evolution of cyclotron radiation from streaming and gyrating electrons in an external magnetic field is analyzed. The nonlinear dynamics of both the fields and the particles are treated fully relativistically and self-consistently. The model includes a background plasma and electrostatic effects. The analytical and numerical results show that a substantial portion of the beam particle energy can be converted to electromagnetic wave energy at frequencies far above the electron cyclotron frequency. In general, the excited radiation can propagate parallel to the magnetic field and, hence, escape gyrothermal absorption at higher cyclotron harmonics. The high-frequency Doppler-shifted cyclotron instability can have saturation efficiencies far higher than those associated with well-known instabilities of the electron cyclotron maser type. Although the analysis is general, the possibility of using this model to explain the intense radio emission observed from the sun is explored in detail.

Vlahos, Loukas↗
DOE OSTI2024

Density fluctuation statistics and turbulence spreading at the edge of L–mode plasmas

Long-wavelength density fluctuations ($k{\rho _i}$ <1) are studied using beam emission spectroscopy (BES) at the edge of DIII-D L-mode plasmas (ρ = 0.88–1.1) in scenarios with electron cyclotron heating (ECH) power ramp (P ECH up to 1.5 MW), neutral beam injection (NBI) power ramp (P NBI up to 2.5 MW), and injected torque scan (-1 < T inj <0.6 Nm). We find that broadband turbulent density fluctuations (ƒ ~ 20–120 kHz) have a non-Gaussian distribution. The skewness of $\delta n/n$ changes sign from negative at ρ < 0.95–0.97 to positive at ρ > 0.97, indicating the prevalence of density 'voids' at inner radii and density 'blobs' at outer radii and outside of the separatrix. The turbulence intensity flux $\left\langle {{{\tilde v}_{\text{r}}}{{\tilde n}^2}} \right\rangle$ is calculated to characterize turbulence spreading at the plasma edge. During ECH/NBI power ramps and at counter-I p injected torque, $\left\langle {{{\tilde v}_{\text{r}}}{{\tilde n}^2}} \right\rangle$ is directed inward inside the separatrix, which is evidence of inward spreading of turbulence intensity from the edge gradient region caused by the inner propagation of density 'voids'. Significantly weaker $\left\langle {{{\tilde v}_{\text{r}}}{{\tilde n}^2}} \right\rangle$ is observed with co-I p torque. A correlation between co-I p torque, turbulence intensity $\delta n/n$ at ρ = 0.97, and increased srape-off layer (SOL) heat flux decay length ${\lambda _q}$ is found in the torque scan scenario, showing that edge turbulence plays a material role in determining the SOL conditions and heat flux width.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2002

Measurement of Metastable Lifetimes of Highly-Charged Ions

The present work is part of a series of measurements of metastable lifetimes of highly-charged ions (HCIs) which contribute to optical absorption, emission and energy balance in the Interstellar Medium (ISM), stellar atmospheres, etc. Measurements were carried out using the 14-GHz electron cyclotron resonance ion source (ECRIS) at the JPL HCI facility. The ECR provides useful currents of charge states such as C(sup(1-6)+), Mg(sup(1-6)+) and Fe(sup(1-17)+). In this work the HCI beam is focused into a Kingdon electrostatic ion trap for measuring lifetimes via optical decays.

Smith, Steven J.↗