Exchange ions produced by an ion propulsion system

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76181/1/AIAA-2001-968-867.pd

A Bevalac Calibration of a Scintillating Optical Fiber Hodoscope for Possible use on the Advanced Composition Explorer

As part of instrument definition activities for the Advanced Composition Explorer (ACE) we are evaluating a hodoscope comprised of scintillating fibers for possible use in the Cosmic Ray Isotope Spectrometer (CRIS). The hodoscope would determine the trajectories of individual cosmic ray nuclei which stop in the silicon solid state telescopes in CRIS. We report a preliminary analysis of data from a Dec., 1990 Bevalac calibration of a CRIS test model which consisted of a scintillating fiber hodosccpe, utilizing 200mm, square cross section scintillating fibers, and silicon detectors for dE/dx-Erot measurements. The positional resolution obtained in our preliminary data analysis is -60μm for angles from 0-30°. The detection efficiency for iron and silicon nuclei was determined to be >99% for beam angles of ≥ 20°

Hard X-ray variability of the black-hole candidate GRO J0422+32 during its 1992 outburst

We have studied the hard X-ray variability of the soft X-ray transient GRO J0422+32 with BATSE in the 20-100 keV energy band. Our analysis covers 180 days following the first X-ray detection of the source on 1992 August 5, fully covering its primary and secondary X-ray outburst. We computed power density spectra (PDSs) in the 20-50, 50-100, and 20-100 keV energy bands, in the frequency interval 0.002-0.488 Hz. The PDSs of GRO J0422+32 are approximately flat up to a break frequency, and decay as a power law above, with index ~1. The canonical anticorrelation between the break frequency and the power density at the break, observed in Cyg X-1 and other BHCs in the low state, is not observed in the PDSs of GRO J0422+32. We compare our results with those of similar variability studies of Cyg X-1. The relation between the spectral slope and the amplitude of the X-ray variations of GRO J0422+32 is similar to that of Cyg X-1; however, the relation between the hard X-ray flux and the amplitude of its variation is opposite to what has been found in Cyg X-1. Phase lags between the X-ray flux variations of GRO J0422+32 at high and low photon energies, could only be derived during the first 30 days of its outburst. During this period, the variations in the 50-100 keV lag those in the 20-50 keV energy band by an approximately constant phase difference of 0.039(3) rad in the frequency interval 0.02-0.20 Hz.Comment: 33 pages, including 14 postscript figures, AASTEX. To appear in ApJ 1999, March 1, vol. 513 #

Correlation Between BATSE Hard X-ray Spectral and Timing Properties of Cygnus X-1

We have analyzed approximately 1100 days of Cygnus X-1 hard X-ray data obtained with BATSE to study its rapid variability. We find for the first time correlations between the slope of the spectrum and the hard X-ray intensity, and between the spectral slope and the amplitude of the rapid variations of the hard X-ray flux. We compare our results with expectations from current theories of accretion onto black holes.Comment: 17 pages, 3 Postscript figures, uses aasms4.sty. Accepted for publication in Astrophysical Journal Letter

Preliminary interpretation of Titan plasma interaction as observed by the Cassini Plasma Spectrometer: Comparisons with Voyager 1

The Cassini Plasma Spectrometer (CAPS) instrument observed the plasma environment at Titan during the Cassini orbiter's TA encounter on October 26, 2004. Titan was in Saturn's magnetosphere during the Voyager 1 flyby and also during the TA encounter. CAPS measurements from this encounter are compared with measurements made by the Voyager 1 Plasma Science Instrument (PLS). The comparisons focus on the composition and nature of ambient and pickup ions. They lead to: A) the major ion components of Saturn's magnetosphere in the vicinity of Titan are H+, H-2(+) and O+/CH4+ ions; B) finite gyroradius effects are apparent in ambient O+ ions as the result of their absorption by Titan's extended atmosphere; C) the principal pickup ions are composed of H+, H-2(+), N+/CH2+, CH4+, and N-2(+); D) the pickup ions are in narrow energy ranges; and E) there is clear evidence of the slowing down of background ions due to pickup ion mass loading

Cassini Plasma Spectrometer and hybrid model study on Titan's interaction: Effect of oxygen ions

During the Cassini Titan flyby on 2 July 2006 (T15), Titan was surrounded by a magnetospheric plasma flow with density about 0.1 cm‑3 as measured by Cassini Plasma Spectrometer (CAPS). A very low fraction of water group ions (O+) was detected in the flow dominated by hydrogen ions. We show that Titan's plasma interaction can be highly sensitive to the small fraction of oxygen ions in the magnetospheric flow. The ion quantities of the magnetospheric flow during the flyby were obtained from numerical moments calculated from the CAPS measurements; the average ambient magnetic field was determined using the Cassini magnetometer data. We simulated the flyby using a global hybrid model; the water group abundance in the flow was varied in three simulation runs. Based on the simulation results, the oxygen content has an especially notable effect on the extent of Titan's induced magnetosphere. A multi-instrument analysis was performed comparing with the simulations, whereby a comprehensive picture of the plasma properties around Titan during this flyby was obtained. Comparisons between the hybrid model simulations and Cassini measurements during the flyby point toward O+ density in the undisturbed magnetospheric flow having been around 0.008 cm‑3, which would have accounted for one half of the dynamic pressure of the flow.Fil: Sillanpää, I.. Southwest Research Institute; Estados UnidosFil: Young, D. T.. Southwest Research Institute; Estados UnidosFil: Crary, F.. Southwest Research Institute; Estados UnidosFil: Thomsen, M.. Los Alamos National Laboratory,; Estados UnidosFil: Reisenfelc, D.. University of Montana; Estados UnidosFil: Wahlund, J. E.. Swedish Institute of Space Physics; SueciaFil: Bertucci, Cesar. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Kallio, E.. Finnish Meteorological Institute,; FinlandiaFil: Jarvinen, R.. Finnish Meteorological Institute; FinlandiaFil: Janhunen, P.. Finnish Meteorological Institute,; Finlandi

Compilation of extended recursion in call-by-value functional languages

This paper formalizes and proves correct a compilation scheme for mutually-recursive definitions in call-by-value functional languages. This scheme supports a wider range of recursive definitions than previous methods. We formalize our technique as a translation scheme to a lambda-calculus featuring in-place update of memory blocks, and prove the translation to be correct.Comment: 62 pages, uses pi

Hard X-ray lags in GRO J1719-24

We have used the Fourier cross spectra of GRO J1719-24, as obtained with BATSE, to estimate the phase lags between the X-ray flux variations in the 20--50 and 50--100 keV energy bands as a function of Fourier frequency in the interval 0.002--0.488 Hz. Our analysis covers the entire ~80 day X-ray outburst of this black-hole candidate, following the first X-ray detection on 1993 September 25. The X-ray variations in the 50--100 keV band lag those in the 20--50 keV energy band by an approximately constant phase difference of 0.072 +/- 0.010 rad in the frequency interval 0.02--0.20 Hz. The peak phase lags in the interval 0.02--0.20 Hz are about twice those of Cyg X-1 and GRO J0422+32.These results are consistent with models for Comptonization regions composed of extended non-uniform clouds around the central source.Comment: 10 pages, including 4 postscript figures, AASTEX. Accepted for publication by Ap