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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 307 records · Page 17
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NASA NTRS2023

A Data-driven, Physics-based Transport Model of Solar Energetic Particles Accelerated by Coronal Mass Ejection Shocks Propagating through the Solar Coronal and Heliospheric Magnetic Fields

In an effort to develop computational tools for predicting radiation hazards from solar energetic particles (SEPs), we have created a data-driven physics-based particle transport model to calculate the injection, acceleration, and propagation of SEPs from coronal mass ejection (CME) shocks traversing through the solar corona and interplanetary magnetic fields. The model runs on an input of corona and heliospheric plasma and magnetic field configuration from a magnetohydrodynamic model driven by solar photospheric magnetic field measurements superposed with observed CME shocks determined from coronagraph images. SEP source particles are injected at the shock using the result of diffusive shock acceleration formulation from a characteristic obliquity-dependent injection from a heated solar wind thermal tail population. With several advanced computation techniques involving stochastic simulation and integration, the model obtains the particle intensity at any location in interplanetary space through the rigorous solution to the time-dependent 5D focus transport equation in the phase space that includes perpendicular diffusion. We apply the model to the 2011 November 3 CME event. The calculation results reproduce multispacecraft SEP observations at Earth and STEREO-B reasonably well without normalization of particle flux. The observations at STEREO-A can be reproduced by rescaling particle energy or modified energy dependence of particle diffusion coefficients. This circumsolar SEP event seen by spacecraft at Earth, STEREO-A, and STEREO-B at widely separated longitudes can be explained by diffusive shock acceleration by a single CME shock with a moderate speed.

Solar energetic particles↗
NASA NTRS2005

Cassini Radio and Plasma Wave Observations at Saturn

Results are presented from the Cassini radio and plasma wave instrument during the approach and first few orbits around Saturn. During the approach the intensity modulation of Saturn Kilometric Radiation (SKR) showed that the radio rotation period of Saturn has increased to 10 hr 45 min plus or minus 36 sec, about 6 min longer than measured by Voyager in 1980-81. Also, many intense impulsive radio signals called Saturn Electrostatic Discharges (SEDs) were detected from saturnian lightning, starting as far as 1.08 AU from Saturn, much farther than terrestrial lightning can be detected from Earth. Some of the SED episodes have been linked to cloud systems observed in Saturn s atmosphere by the Cassini imaging system. Within the magnetosphere plasma wave emissions have been used to construct an electron density profile through the inner region of the magnetosphere. With decreasing radial distance the electron density increases gradually to a peak of about 100 per cubic centimeter near the outer edge of the A ring, and then drops precipitously to values as low as .03 per cubic centimeter over the rings. Numerous nearly monochromatic whistler-mode emissions were observed as the spacecraft passed over the rings that are believed to be produced by meteoroid impacts on the rings. Whistlermode emissions, similar to terrestrial auroral hiss were also observed over the rings, indicating that an electrodynamic interaction, similar to auroral particle acceleration, may be occurring in or near the rings. During the Titan flybys Langmuir probe and plasma wave measurements provided observations of the density and temperature in Titan's ionosphere.

Gurnett, D. A.↗
NASA NTRS1974

Solar particles /observations, relationship to the sun acceleration, interplanetary medium/

The major features of the propagation of flare particles in the interplanetary medium are discussed in terms of the classic well-behaved flare having unique impulsive injection and a smooth time profile. Topics include flare events, their frequency of occurrence, development of a typical event, energy spectra, proton and electron types, charge and isotopic composition, solar flares and particle accelerations, radio and X-ray observations, the Fermi mechanism, the betatron mechanism, acceleration models, plasma instabilities, two-stage acceleration, propagation mechanisms, the anisotropic stage, the diffusive stage, and the convection and energy loss stage.

Mcdonald, F. B.↗
NASA NTRS1975

Flux limit on cosmic ray acceleration by strong spherical pulsar waves

The study investigates the acceleration of cosmic rays by superrelativistic plasma waves. The pulsar wave field imposed upon the particles is that of a magnetic dipole wave including azimuthal dependence and near field terms. The refractive index of the plasma is assumed to be constant everywhere. Two distinct zones appear: in the near zone spherical effects dominate, particles may be decelerated; in the far zone the results for the motion differ noticeably from the vacuum case. From a WBK-like treatment for a spherical S wave, it is concluded that for a wave solution to be valid even near the light cylinder, the wave can carry a sufficiently small particle flux.

Asseo, E.↗
NASA NTRS1981

The hot plasma environment and floating potentials of an electron-beam-emitting rocket in the ionosphere

The plasma environment surrounding the Echo III accelerator payload is examined with an extensive array of particle sensors. Suprathermal electrons are produced isotropically around the payload during the gun firings and decay away in approximately 32 ms. The largest directional intensities of this component are observed at the higher altitudes. Quick echo electrons are also observed to produce suprathermal electrons when they encounter the payload. The hot electrons surrounding the accelerator payload during gun injections bring sufficient charge to the payload to neutralize it provided the loss of charge by secondary production on the payload skin is small. Since the hot population exists for tens of milliseconds after the gun turnoff, it results in driving the payload up to 4 volts negative during this time. Quick echo electrons creating suprathermal electrons around the payload also drive the payload to a few volts negative.

Arnoldy, R. L.↗
NASA NTRS1989

High-speed flows of H(+) and He(2+) ions at the magnetosphere

Observations of high-speed flows of H(+) and He(2+) ions obtained by the hot plasma composition experiment on AMPTE/CCE provide direct support for the single-particle approach to acceleration in current layers. These high-speed flows are attributed to single-fluid momentum balance across a magnetopause with a normal magnetic field and a tangential electric field. The flow speeds of the two ion species are found to be approximately equal.

Paschmann, G.↗
NASA NTRS1989

Cometary environments; Proceedings of Symposium 5, Workshop IV, and Topical Meeting of the 27th COSPAR Plenary Meeting, Espoo, Finland, July 18-29, 1988

Papers on the environment of comets are presented, covering topics such as constraints on the interstellar dust model of comet dust, dust particles and comet nuclei, models of cometary nuclei, subliming gas in the near-nuclear layer of the comet coma, the nucleus and rotation of Comet Halley, the surface albedo of comet nuclei, observational studies on Comet Halley, comet simulations, comet ion composition, and chemical abundances in comets. Additional topics include the O 1D and H2O production rate from comets, collisional coma models, the gas coma of Comet Giacobini-Zinner, IR properties of rough comet grains, studies of Comet Halley by Giotto, the impact of large dust particles on the Vega spacecraft, and carbonaceous materials as components of comet dust. Also, consideration is given to comet plasma boundaries, the comet ionopause, the solar wind-comet interaction, MHD turbulence and particle acceleration in a mass-loaded solar wind, combined first and second order Fermi acceleration at comets, discrete wave packets upstream from the earth and comets, and the visual appearance of comets under varying solar wind conditions.

Gombosi, T. I.↗
NASA NTRS2012

Radiation from Accelerated Particles in Shocks and Reconnections

We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic jets propagating into an unmagnetized plasmas. Strong magnetic fields generated in the trailing shock contribute to the electrons transverse deflection and acceleration. We have calculated, self-consistently, the radiation from electrons accelerated in the turbulent magnetic fields. We found that the synthetic spectra depend on the Lorentz factor of the jet, its thermal temperature and strength of the generated magnetic fields. The properties of the radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants

Nishikawa, K.-I.↗
NASA NTRS1983

Lorentz forces on the dust in Jupiter's ring

The paths of dust particles in the Jovian ring are investigated using a numerical integration program, including the acceleration due to gravity and the Lorentz and drag accelerations arising from the motions of the charged dust through the Jovian plasma. It is determined that the orbit of a 2.5 micron radius spherical dust particle with a density of 2 g/cu cm -10V will become significantly perturbed. The ring will tend to warp northwards near 130-160 deg longitude, with the maximum excursion of the Jupiter ring grains equalling about 0.1 deg (consistent with a distance of 220 km above the equatorial plane). It is found that either the particles are larger or the voltages on them less than what has been determined by previous investigators, while the plasma near the ring may be considerably cooler than was estimated. Calculations show that particles of 0.3 micron with -10 V potentials are spread from 1.68-1.98 of the radius of Jupiter and inclined up to 7 deg out of the equatorial plane. The paths of these particles do not follow Keplerian orbits, and the particle positions are not symmetric about the equatorial plane. Particles of 0.4 micron radius have less asymmetric orbits than 0.3 micron particles, while particles less than 0.2 micron are perturbed into Jupiter cloudtops within a few tens of hours.

Consolmagno, G. J.↗
NASA NTRS1986

Unstable-magnetic-drift waves in a plasma with temperature anisotropy

It is pointed out that under certain conditions, such as a weak electron temperature anisotropy, the magnetic-drift wave instability can become rather important, and the growth rate can be greater than the ion gyrofrequency when the scale length of the density gradient is comparable to, or shorter than, the thermal ion gyroradius. The instability is attributed to wave-electron interactions, and the growth rate is far greater than the case investigated by Krall and Rosenbluth (1963) who attributed the instability to wave-ion interactions. The anticipated vanishing of the instability is observed as epsilon sub n/epsilon sub B approaches zero. The presently observed instability may be used to explain the low-frequency fluctuations evidenced by the Active Particle Tracer Explorer Ion Release Module magnetometer measurements, and may contribute to the acceleration of ions along the plasma cometary tail.

Wu, C. S.↗
NASA NTRS1994

High Altitude Plasma Instrument (HAPI) data analysis

The objectives of the Dynamics Explorer mission are to investigate the coupling of energy, mass, and momentum among the earth's magnetosphere, ionosphere, and upper atmosphere. At launch, on August 3, 1981, DE-1 was placed into an elliptical polar orbit having an apogee of 23,130 km to allow global auroral imaging and crossings of auroral field lines at altitudes of several thousand kilometers. At the same time DE-2 was placed into a polar orbit, coplanar with that of DE-1 but with a perigee altitude low enough (309 km) for neutral measurements and an apogee altitude of 1012 km. The DE-1 High Altitude Plasma Instrument (HAPI) provided data on low and medium energy electrons and ions from August 13, 1981 until December 1, 1981, when a high-voltage failure occured. Analysis of HAPI data for the time period of this contract has produced new results on the source mechanisms for electron conical distributions, particle acceleration phenomena in auroral acceleration regions, Birkeland currents throughout the nightside auroral regions, the source region for auroral kilometric radiation (AKR), and plasma injection phenomena in the polar cusp.

Burch, J. L.↗
NASA NTRS2015

Stochastic Acceleration of Ions Driven by Pc1 Wave Packets

The stochastic motion of protons and He(sup +) ions driven by Pc1 wave packets is studied in the context of resonant particle heating. Resonant ion cyclotron heating typically occurs when wave powers exceed 10(exp -4) nT sq/Hz. Gyroresonance breaks the first adiabatic invariant and energizes keV ions. Cherenkov resonances with the electrostatic component of wave packets can also accelerate ions. The main effect of this interaction is to accelerate thermal protons to the local Alfven speed. The dependencies of observable quantities on the wave power and plasma parameters are determined, and estimates for the heating extent and rate of particle heating in these wave-particle interactions are shown to be in reasonable agreement with known empirical data.

stochastic↗
NASA NTRS1999

Plasma Pressure in the Topside Ionosphere

A previous three year NASA-funded project resulted in the first 2-D maps of magnetotail pressure, density and temperature. A proposal to continue the work was declined, but modest funding was provided for one year to ramp down of the work. During the phase-out year, we used a time when 5 DMSP satellites were simultaneously active to produce the first instantaneous partial image of the magnetotail. The results have been submitted to the proceedings of the 1998 Huntsville Meeting on "The New Millennium Magnetosphere: Integrating Imaging, Discrete Observations and Global Simulations". A method of inferring central plasma sheet (CPS) temperature, density, and pressure from ionospheric observations was developed under a previous 3-year grant. These particles properties are calculated from data taken by particle instruments on DMSP satellites. Ion spectra occurring in conjunction with electron acceleration events are excluded. Because of the variability of magnetotail stretching, mapping to the plasma sheet was done using a modified Tsyganenko 1989 magnetic field model adjusted to agree with the actual magnetotail stretch. On May 25, 1997, five DMSP satellites (F10-F14) passed through the southern hemisphere nightside oval within a 19 minute period. Attached is the first magnetotail image, which results from applying our technique to that data set.

Newell, Patrick T.↗
NASA NTRS1992

High-energy particle acceleration by explosive electromagnetic interaction in an accretion disk

By examining electromagnetic field evolution occurring in an accretion disk around a compact object, we arrive at an explosive mechanism of particle acceleration. Flux-freezing in the differentially rotating disk causes the seed and/or generated magnetic field to wrap up tightly, becoming highly sheared and locally predominantly azimuthal in orientation. We show how asymptotically nonlinear solutions for the electromagnetic fields may arise in isolated plasma blobs as a result of the driving of the fluid equations by the accretion flow. These fields are capable of rapidly accelerating charged particles from the disk. Acceleration through the present mechanism from AGN can give rise to energies beyond 10 exp 20 eV. Such a mechanism may present an explanation for the extragalactic origin of the most energetic observed cosmic rays.

Haswell, C. A.↗
NASA NTRS1995

Update on the Fire (solar probe) mission study

Since mid-1994 the U.S. and Russia have been studying the technical feasibility of a joint solar probe mission as part of the 'Fire and Ice' concept to explore close to the Sun, and Pluto, together. In the current concept of the 'Fire' mission, separate spacecraft built by each country would be launched together, fly by Jupiter to shed orbital angular momentum and achieve a solar polar orbit, and arrive 3.6 years later at 4 and 10 R(sub s). The Fire mission would measure basic parameters of the modes of energy and momentum flow and transfer to the coronal plasma that are not observable remotely. Specifically, measurement of magnetic fields, waves, suprathermal particles, and critical features of the plasma particle composition and distribution function would be made from 4 to 30 R(sub s) where the solar wind is known to be accelerated. In addition, the Fire spacecraft should image coronal structures unambiguously and relate the underlying and flown-through structures to plasma characteristics measured in situ. Each country is developing a backup plan to pursue the solar probe objectives alone if the other side is unable to carry out its mission.

Jones, W. Veron↗
NASA NTRS1974

Acceleration of solar cosmic rays during chromospheric flares

Using the Fokker-Planck equation, an examination is made of the acceleration of charged particles by fluctuational electric fields caused by the propagation of intense radio emission in the long-wave range. Correlation functions of electric fields near the boundary of plasma instability were computed. The interaction of charged particles with these fields is examined. It is shown that due to the interaction of particles with fluctuational fields, solar cosmic rays can be accelerated to energies of E=100 to 1000 MeV.

Dorman, L. I.↗
NASA NTRS1973

Cosmic-ray generation by pulsars

Electromagnetic and particle energy fluxes are equipartitioned in a superrelativistic plasma wave. The consequences for cosmic-ray acceleration by pulsars are investigated.

Kennel, C. F.↗
NASA NTRS1979

Some problems of pulsar physics

The theories of particle acceleration along polar field lines are reviewed, and the total energization of the charge separated plasma is summarized, when pair creation is absent. The application of these theories and plasma supply to pulsars is discussed, with attention given to the total amount of electron-positron plasma created and its momentum distribution. Various aspects of radiation emission and transport are analyzed, based on a polar current flow model with pair creation, and the phenomenon of marching subpulses is considered. The coronation beaming and the relativistically expanding current sheet models for pulsar emission are also outlined, and the paper concludes with a brief discussion of the relation between the theories of polar flow with pair plasma and the problem of the energization of the Crab Nebula.

Arons, J.↗