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Cosmic ray particle transport in random magnetic fields is analyzed. Data cover particle transport in which q is greater than or equal to 2, and density inhomogeneities propagate in a wavelike fashion with very little dispersion. Physical interpretations rather than mathematical proofs are emphasized.
When the distribution function for energetic particles moving in interplanetary space is expressed in terms of eigenfunctions of an operator which describes pitch angle scattering by random magnetic fields, the familiar phenomenon of diffusion is the dominant solution of the transport equations provided that the spectrum of magnetic fluctuations is not too steep. The present paper describes a novel mode of particle transport when the latter condition is not satisfied (i.e., when the exponent for the spectrum of magnetic fluctuations is greater than 2). In this mode, the density inhomogeneities propagate coherently, in wavelike fashion, and with very little dispersion along the guiding field at a characteristic velocity equal to half the particle speed. The most striking manifestation of this phenomenon is the observed scatter-free propagation of solar flare electrons below 1 MeV.-
Energetic protons and electrons introduced into the vicinity of the synchronous orbit by geomagnetic substorms and observed on ATS 5 at various local times have been analyzed for velocity dispersion effects associated with their longitudinal drift. Particles with energies between about 30 and 200 keV are shown to be produced simultaneously within tens of minutes at local times between about 0000 and 0400 near 6.6 earth radii during substorm activity. Those with energies not less than approximately 75 keV move in longitude in the direction and with the magnitude expected from gradient B drifts. Lower-energy protons and electrons appear at the satellite sooner than expected from their gradient B drifts, as though the observed particles of such energies were not those originally accelerated but were newly produced from or by the higher-energy drifting component.
When the distribution function for energetic particles moving in interplanetary space is expressed in terms of eigenfunctions of an operator which describes pitch-angle scattering by random magnetic fields, the familiar phenomenon of diffusion is the dominant solution of the transport equations provided that the spectrum of magnetic fluctuations is not too steep. However, if the power-versus-wavenumber spectrum of the random fields has a spectral index greater than 2, the dominant solution of the same equations is a qualitatively different mode of transport in which density inhomogeneities propagate coherently along the guiding field with a characteristic velocity equal to half the particle speed. The present work, which extends classical transport theory to give a detailed treatment of the new mode, presents explicit formulae which describe the spatial and temporal structure of the coherent disturbance. It is shown that this disturbance evolves asymptotically into a moving Gaussian pulse whose width increases with time.
The photon-noise-limited performance of a radiation detector exposed to a thermal background of temperature T is analyzed by calculating the resulting specific detectivity. Both ideal photon detectors of arbitrary quantum efficiency eta and ideal thermal detectors of arbitrary emissivity eta are considered; and the effects of both shot noise and excess noise are taken into account. The relative contributions of these two sources depend on the quantum efficiency or emissivity of the system. For frequencies nu such that hnu/kT is much less than eta, excess noise can make an appreciable contribution to the total system noise. For the case of the detection of the narrow-band radiation, the specific detectivity is independent of eta in the limit hnu/kT is much less than eta.
Shortly after a strongly anisotropic beam of charged particles is injected along a guiding magnetic field on which is superimposed a small random conponent, the particle density can be represented by a Gaussian profile whose center moves with the coherent velocity and whose width increases with time at a rate controlled by the coefficient of dispersion. Both parameters depend upon the mean free path, which characterizes scattering by the random fields, and the focusing length, which characterizes spatial variations of the guiding field. These dependencies are known explicitly for the coherent velocity. Formulae for coefficient of dispersion are available only in the limits of very weak and very strong focusing. A new expression for coefficient of dispersion, which spans this gap, is presented.
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During the Giotto encounter with comet P/Grigg-Skjellerup, the ion mass spectrometer high intensity spectrometer (IMS-HIS) measured fluxes of ions from about 260,000 before to 86,000 km after closest approach to the comet. Cometary pickup protons were measured both far and also relatively near the comet.
Idaho National Laboratory is the Department of Energy’s (DOE) lead lab for nuclear energy research and is dedicated to supporting the advancement of missions in nuclear energy research, energy and environment, and national security. The laboratory is operated by Battelle Energy Alliance (BEA) and participates both independently and jointly with other labs in the support of work for the DOE and other government organizations. The Information Management department is a key support organization whose purpose is to enable the three key areas supporting the Laboratory mission, Nuclear Energy, National and Homeland Security, and Energy and Environment, are successful. The challenge that we face is having relevant information about what these key areas of the Laboratory are working on and how we can best support them in achieving overall mission success. In addition, one of the major challenges that they face comes with knowing their customers and their customer’s needs so that they can successfully execute on their mission. Technology Application Organizations today are dependent on understanding their customers and competitors so that they can respond accordingly, but this can be a difficult and vexing challenge. Customers do not always reveal all of their needs and competitors rarely come out and reveal what they are doing, but this does not mean that hints about their plans are not abundant in information that is readily available. The challenge has always been how to keep track of all that is happening and converting that into useful information. Taking the lead from the “Screwball Division” from World War II, we have the tools available to automate this process and start to mine the Internet to get clues of what our customers and competitors are actively working on. By looking at what is being said and relating that to what else is being said, we can build competitive intelligence and act upon this to further our organizational objectives.
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A new system for measuring the SNS ion beam longitudinal profile was recently upgraded to operational status. The hardware for this device was developed and delivered by Institute of Nuclear Research to the SNS as a part of its initial construction. The supplied LabVIEW user interface software was intended for proof-of-operation and initial setup of the instrument. While satisfactory for this, it was tedious to use in a practical context and lacked any form of interface to the SNS EPICS based control system. This paper will describe the software features added to make this instrument both easily tunable to the prevalent beam conditions by system engineers and easily usable by accelerator physicists only interested in its output data.
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