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Results for “drift resonance”

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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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Modulation of energetic particle fluxes by a mixed mode of transverse and compressional waves

Modulation characteristics of particle fluxes in the presence of a mixed mode of compressional and transverse magnetic waves at hydromagnetic frequencies are investigated through kinetic perturbation of the distribution function. The magnetospheric medium where the particles are modulated contains both the magnetic and pressure gradients. The modulation features are found to be strongly dependent on the energy and pitch angle of the particles. Drifting particles can resonate with waves whose phase velocities are close to their drift velocities. When this occurs, the modulation amplitudes become significantly large and large phase shifts will occur. It is pointed out that resonance is important for particles with mid pitch angles (40-70 deg). The phase shift between the particle modulations and the magnetic field oscillations are strongly controlled by the combined effects of transverse and compressional wave components and/or the occurrence of drift resonance. Numerical calculations are performed using the dispersion relation of drift mirror Alfven waves as an example of waves with both compressional and transverse components.

Lin, C. S.↗
NASA NTRS2016

OSSOS. IV. Discovery of a Dwarf Planet Candidate in the 9:2 Resonance with Neptune

We report the discovery and orbit of a new dwarf planet candidate, 2015 RR245, by the Outer Solar System Origins Survey (OSSOS). The orbit of 2015 RR245 is eccentric (e 0.586), with a semimajor axis near 82 au, yielding a perihelion distance of 34 au. 2015 RR245 has g - r 0.59 +/- 0.11 and absolute magnitude Hr 3.6 +/- 0.1; for an assumed albedo of pV 12, the object has a diameter of approximately 670 km. Based on astrometric measurements from OSSOS and Pan-STARRS1, we find that 2015 RR245 is securely trapped on ten-megayear timescales in the 9:2 mean-motion resonance with Neptune. It is the first trans-Neptunian object (TNO) identied in this resonance. On hundred-megayear timescales, particles in 2015 RR245-like orbits depart and sometimes return to the resonance, indicating that 2015 RR245 likely forms part of the long-lived metastable population of distant TNOs that drift between resonance sticking and actively scattering via gravitational encounters with Neptune. The discovery of a 9:2 TNO stresses the role of resonances in the long-term evolution of objects in the scattering disk and reinforces the view that distant resonances are heavily populated in the current solar system. This object further motivates detailed modeling of the transient sticking population.

Bannister, Michele T.↗
NASA NTRS2017

Global Observations of Magnetospheric High-m Poloidal Waves During the 22 June 2015 Magnetic Storm

We report global observations of high-m poloidal waves during the recovery phase of the 22 June 2015 magnetic storm from a constellation of widely spaced satellites of five missions including Magnetospheric Multiscale (MMS), Van Allen Probes, Time History of Events and Macroscale Interactions during Substorm (THEMIS), Cluster, and Geostationary Operational Environmental Satellites (GOES). The combined observations demonstrate the global spatial extent of storm time poloidal waves. MMS observations confirm high azimuthal wave numbers (m approximately 100). Mode identification indicates the waves are associated with the second harmonic of field line resonances. The wave frequencies exhibit a decreasing trend as L increases, distinguishing them from the single-frequency global poloidal modes normally observed during quiet times. Detailed examination of the instantaneous frequency reveals discrete spatial structures with step-like frequency changes along L. Each discrete L shell has a steady wave frequency and spans about 1 RE, suggesting that there exist a discrete number of drift-bounce resonance regions across L shells during storm times.

Le, G.↗
NASA NTRS1993

Loss of ring current O(+) ions due to interaction with Pc 5 waves

A test particle code is used here to investigate ring current ion interaction with Pc 5 waves, combined with convection and corotation electric fields, with emphasis on the loss of O(+) ions over the dayside magnetosphere. A new loss mechanism for the O(+) ions due to the combined effects of convection and corotation electric fields and interactions with Pc 5 waves via a magnetic drift-bound resonance is presented. For given fields, whether a particle gains or losses energy depends on its initial kinetic energy, pitch angle at the equatorial plane, and the position of its guiding center with respect to the azimuthal phase of the wave. The ring current O(+) ions show a dispersion in energies and L values with decreasing local time across the dayside, and a bulk shift to lower energies and higher L values. Due to interaction with the Pc 5 waves, the particle's kinetic energy can drop below that required to overcome the convection potential and the particle is lost to the dayside magnetopause by a sunward E x B drift.

Li, Xinlin↗
NASA NTRS1976

Effects of a magnetic field gradient on the lower hybrid drift instability

The effect of a magnetic field gradient on the lower hybrid drift instability is examined in the low drift velocity regime (i.e., of the order of the ion thermal velocity). The theoretical model includes density and temperature gradients, and considers only waves propagating perpendicular to the ambient magnetic field with wavelengths of the order of the electron Larmor radius. It is found, for the case of a finite ratio of the electron pressure to the magnetic field pressure, that a magnetic gradient drift-wave resonance can be important and is stabilizing or destabilizing depending upon the physical conditions. Substantial plasma heating and a large anomalous resistivity can also occur.

Huba, J. D.↗
NASA NTRS1990

Ion flux oscillations associated with a radially polarized transverse Pc 5 magnetic pulsation

The AMPTE CCE spacecraft observed a transverse Pc 5 magnetic pulsation (period of about 200 s) at 2155-2310 UT on November 20, 1985, at a radial distance of 5.7 - 7.0 earth radii, at a magnetic latitude of 1.2 - 19 deg, and near 1300 magnetic local time. The magnetic pulsation exhibits properties consistent with a standing Alfven wave with a second-harmonic standing structure along the ambient magnetic field. The amplitude and the phase of the flux pulsation are found to be a function of the particle detector look direction and the particle energy. The observed energy dependence of the shift is interpreted as the result of a drift-bounce resonance of the ions with the wave. From this interpretation it follows that the wave propagated westward with an azimuthal wave number of approximately 100. Thus the study demonstrates that particle data can be useful for determining the spatial structure of some types of ULF waves.

Takahashi, K.↗
NASA NTRS1996

Wide Angle, Single Screen, Gridded Square-Loop Frequency Selective Surface for Diplexing Two Closely Separated Frequency Bands

The design and performance of a wide angle, single screen, frequency selective surface (FSS) with gridded square-loop path elements are described for diplexing closely separated signal bands, for example, X- and Ku-band signals in an Orbiting Very Long Baseline Interferometer (OVLBI) earth station reflector antenna system, as well as other applications such as military and commercial communications via satellites. Excellent agreement is obtained between the predicted and measured results of this FSS design using the gridded square-loop patch elements sandwiched between 0.0889 cm thick tetrafluoroethylene fluorocarbon polymer (PTFE) slabs. Resonant frequency drift is reduced by 1 GHz with an incidence angle from 0 deg normal to 40 deg from normal.

Wu, Te-Kao↗
NASA NTRS2007

Procedures for Tuning a Multiresonator Photonic Filter

Two procedures have been devised for tuning a photonic filter that comprises multiple whispering-gallery mode (WGM) disk resonators. As used here, tuning signifies locking the filter to a specific laser frequency and configuring the filter to obtain a desired high-order transfer function. The main problem in tuning such a filter is how to select the correct relative loading of the resonators to realize a prescribed filter function. The first of the two procedures solves this problem. As temperature gradients develop during operation, the spectra of individual resonators tend to drift, primarily because of the thermorefractive effect. Thus, there arises the additional problem of how to adjust the tuning during operation to maintain the desired transfer function. The second of the two procedures solves this problem. To implement the procedures, it is necessary to incorporate the resonators into an apparatus like that of Figure 1. In this apparatus, the spectrum of each resonator can be adjusted individually, via the electro-optical effect, by adjusting a bias voltage applied to that resonator. In addition, the positions of the coupling prisms and resonators can be adjusted to increase or reduce the gaps between them, thereby reducing or increasing, respectively, the optical coupling between them. The optical power (Pi) in resonator i is monitored by use of a tracking photodiode. Another tracking diode monitors the power reflected from the input terminal (Pr), and still others monitor the input power (Pin) and output power (Po). The readings of these photodiodes are used to guide the tuning adjustments described in this paper.

Matsko, Andrey↗
NASA NTRS1976

Simultaneous Pc 1 observations by the synchronous satellite ATS-1 and ground stations - Implications concerning IPDP generation mechanisms

Results are presented for an experimental study designed to examine the properties of Pc 1 activity observed simultaneously at ATS 1 and two Canadian ground stations. The Pc 1 activity is found to follow substorm expansion phase onsets and to occur most frequently at dusk. Dynamic spectra waves at both ground stations are that of IPDP (Intervals of Pulsations Diminishing by Period) type Pc 1. A previously proposed mechanism to explain IPDP generation, which required a rapid increase in the equatorial magnetic field to produce IPDP, is inconsistent with the dynamic spectra and magnetic field observations. Either purely azimuthal or a combination of azimuthal and radial inward drift of energetic resonant protons is an equally plausible mechanism to explain IPDP generation.

Bossen, M.↗
NASA NTRSDate not supplied

Artemis I Liftoff Measurements Issues and Corrections

The SLS rocket was instrumented to collect liftoff environment data during Artemis I launch. The instruments were microphones and pressure transducers. Most data were acceptable for analysis, but required corrections for port resonance, mean signal drift, data system delays, and data spikes. The data were all transmitted via telemetry and in this process some of the measurements experienced unexpectedly long gaps in the data stream. A time validated reconstruction algorithm failed when encountering the long gaps and required use of data from a simpler reconstruction process, with manually inserted data delay corrections. This paper discusses the issues and the corrections that were necessary for the launch data to determine the true physics of the acoustics occurring during launch.

environments↗
NASA NTRSDate not supplied

Artemis I Liftoff Measurements Issues and Corrections

The SLS rocket was instrumented to collect liftoff environment data during Artemis I launch. The instruments were microphones and pressure transducers. Most data were acceptable for analysis, but required corrections for port resonance, mean signal drift, data system delays, and data spikes. The data were all transmitted via telemetry and in this process some of the measurements experienced unexpectedly long gaps in the data stream. A time validated reconstruction algorithm failed when encountering the long gaps and required use of data from a simpler reconstruction process, with manually inserted data delay corrections. This paper discusses the issues and the corrections that were necessary for the launch data to determine the true physics of the acoustics occurring during launch.

environments↗
NASA NTRS1993

Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC

We model the rapid (about 1 min) formation of a new electron radiation belt at L about or = 2.5 that resulted from the Storm Sudden Commencement (SSC) of March 24, 1991 as observed by the Combined Release and Radiation Effects Satellite (CRRES) satellite. Guided by the observed electric and magnetic fields, we represent the time-dependent magnetospheric electric field during the SSC by an asymmetric bipolar pulse that is associated with the compression and relaxation of the Earth's magnetic field. We follow the electrons using a relativistic guiding center code. The test-particle simulations show that electrons with energies of a few MeV at L greater than 6 were energized up to 40 MeV and transported to L about or = 2.5 during a fraction of their drift period. The energization process conserves the first adiabatic invariant and is enhanced due to resonance of the electron drift motion with the time-varying electric field. Our simulation results, with an initial W(exp -8) energy flux spectra, reproduce the observed electron drift echoes and show that the interplanetary shock impacted the magnetosphere between 1500 and 1800 MLT.

Li, Xinlin↗
NASA NTRS1993

Ion mixing in the plasma sheet boundary layer by drift instabilities

The linear stability properties of collisionless drift instabilities are analyzed in a Harris equilibrium model of the plasma sheet boundary layer (PSBL). The strearmng ions with drift-type instabilities driven in the PSBL are considered. The fluid approximation leads to growth but predicts that the mode width approaches the gyroradius of the energetic ions. Thus an integral equation theory for the modes is developed taking into account that in the PSBL the curvature drift is weak compared with the grad-B drift. The exact wave particle resonance is kept in the nonlocal response functions. Plasma density, temperature, and magnetic gradient drift motions are taken into account. The drift modes produce an anomalous cross-field momentum transport mixing the PSBL ions on the time scale of tens of seconds. A nonlinear simulation is performed which shows the coalescence of the small scale, fast growing modes into large-scale vortices. The relation between these collective modes and plasma sheet transport phenomena is discussed including the comparison with the competing plasma mixing from single-particle stochasticity.

Horton, W.↗
NASA NTRS1979

Past obliquity oscillations of Mars - The role of the Tharsis uplift

The paper deals with possible ancient variations of the obliquity of Mars. Consideration of data on internal differentiation, Tharsis uplift and crustal phenomena, mantle convection, and eigenfrequencies and mean motion suggest that (1) differentiation with core formation decreased the primeval spin precession constant (alpha) by 4-5%, driving it through resonance with the j = 2 orbital term; (2) a combination of geophysical processes caused alpha to drift back and forth through resonance with the j = 2 orbital term during part of Mars' history; (3) this situation was turned off by the Tharsis uplift, which drove alpha away from j = 2 resonance and possibly through the j = 26 resonance. The consequences of such events for the planet's obliquity are analyzed. Various types of motions are calculated, demonstrating the sensitivity of the obliquity to passage through resonance with such minor orbital terms.

Ward, W. R.↗
NASA NTRS1985

Cosmic-ray transport in the galactic magnetosphere

It is advantageous to regard cosmic rays as the constitutent particles of the Galactic radiation belts and cosmic ray energization as a consequence of inward radial diffusion in the quasi-dipolar Galactic magnetosphere. This process occurs in addition to Fermi acceleration. The purpose of this work is to explore a magnetospheric explanation for the elevation of Galactic charged particles to cosmic ray energies. The magnetosphere that is of interest in this context is not a planetary magnetosphere but a galactic magnetosphere entirely analogous to those inferred from radio observations of distant galaxies. It is the magnetosphere of the Milky Way. Cosmic rays are (by this interpretation) the charged particles that constitute the radiation belts of the Galactic magnetosphere. Thus, the mechanism by which charged particles attain cosmic-ray energies is presumable the mechanism by which radiation-belt particles attain high energies in more familiar magnetosphere, i.e., the radial diffusion associated with magnetic disturbances that contain spectral power resonant with the azimuthal drift of the particles.

Schulz, M.↗
NASA NTRS1993

Dichroic Design for the Orbiting VLBI Earth Station Antenna

In this paper the design and performance of a single screen frequency selective surface with gridded square loop patch elements are described for diplexing the X-and Ku-band signals in an Orbiting Very Long Baseline Interferometer (OVLBI) earth station reflector antenna system.

gridded square element resonant frequency drift Or↗