Publication archive

Publication archive

High-speed flows in the inner central plasma sheet (first reported by Baumjohann et al. (1990) are studied, together with the concurrent behavior of the plasma and magnetic field, by using AMPTE/IRM data from about 9 to 19 R(E) in the earth magnetotail. The conclusions drawn from the detailed analysis of a representative event are reinforced by a superposed epoch analysis applied on two years of data. The high-speed flows organize themselves in 10-min time scale flow enhancements called here bursty-bulk flow (BBF) events. Both temporal and spatial effects are responsible for their bursty nature. The flow velocity exhibits peaks of very large amplitude with a characteristic time scale of the order of a minute, which are usually associated with magnetic field dipolarizations and ion temeperature increases. The BBFs represent intervals of enhanced earthward convection and energy transport per unit area in the y-z GSM direction of the order of 5 x 10 exp 19 ergs/R(E-squared).
Published: 02 March 1992
Pages: 485
Publisher: John Wiley and Sons
ISBN: 0-471-61011-9
Published: 01 January 1991
The occurrence rates and typical characteristics of high-speed ion flows with velocities of 400-600 km/s are determined on the basis of the analysis of a large quantity of ion moments and magnetic field measurements acquired from the AMTE/IRM satellite data. It is determined that the occurrence rates in the plasma sheet boundary layer, the outer central plasma sheet and the neutral sheet neighborhood have 4:1:2 ratio, and they increase with AE in all three regions when going from low to moderate activity; that the largest occurrence rates are near the midnight meridian at the largest radial distances accessible to IRM; and that the high-speed flow occurrence rates and ion densities are anticorrelated. It is also determined that the high-speed flows are bursty, and their angular distribution is strongly peaked in the sunward direction. No tailward high speed ion flow was detected. Correlation between the obtained results and the existing models and theories is discussed.
Published: 02 March 1990
Pages: 577
Publisher: Pergamon Press
ISBN: 0-08-034859-9
Published: 01 January 1990
Present knowledge on gamma radiation that originates from cosmic-ray interactions with gas and photons in the ISM is reviewed. Basic principles of such radiation and the main observational results are described. The significance of the findings for molecular gas studies and cosmic ray studies is discussed. Present understanding of radiation from gamma-ray point sources is briefly addressed, emphasizing the possible diffuse nature of these sources.
Published: 16 June 1989
A statistical study on the behaviors of ion and electron moments in the central plasma sheet was carried out using tail data obtained by the three-dimensional plasma instrument on board the AMPTE/IRM satellite in 1986. Results show that the ion temperature increases with increasing magnetic activity and the ion density decreases during disturbed intervals, except in the neutral sheet neighborhood at smaller radial distances. The ion and electron temperatures (Ti and Te, respectively) in the central plasma sheet were found to be highly correlated, with the Ti/Te ratio being constant over a wide range of temperatures and about twice as large as in the distant tail. The average ion flow speeds in the central plasma sheet (below 100 km/sec) are nearly identical to those found in the plasma sheet boundary layer, but their distribution functions for these regions are quite different.
Published: 02 May 1989
Refractory metal Nb/Al/Al-oxide/Al/Nb junctions are shown to be sensitive to 6-keV X-rays over the temperature range from 2.8 to 1.4 K. For such junctions, which have an observed minimum ionizing energy of 12 MeV, a limiting energy resolution of 8 eV is predicted. Currently an energy resolution of 250 eV is observed at 1.4 K which is primarily dominated by system electronic noise. The Nb-based junctions are shown to be very stable with respect to thermal cycling while the nonequilibrium physics can be simply scaled from the theory of Sn junctions. It is concluded that on-chip arrays having a broad band pass and good energy resolution should be feasible to construct.
Published: 15 March 1989
New results on the temporal and spectral characteristics of the high energy gamma ray emission from the Vela pulsar are presented. A new sensitive analysis method using maximum likelihood techniques has been applied to the final COS-B dataset. The whole pulsed flux is found to exhibit long term variability. The energy spectrum of this total emission cannot be described by a single power law and the data show strong evidence for a spectral break at approximately 300 MeV. Five discrete emission regions within the pulsar light-curve have been identified, with the spectral characteristics and long term behavior being different. These results support the idea that various source regions simultaneously exist in the pulsar magnetosphere and that the physical processes generating the gamma rays in these sites differ with the location.
Published: 15 October 1988
A statistical survey was performed on ion moments (including data on bulk velocity, ion beta, the ratio between the ion pressure and magnetic pressure, and ion temperature anisotropy) near the plasma sheet boundary layer and the immediately adjacent outer central plasma sheet, using four months of tail data obtained by the three-dimensional plasma instrument aboard the AMPTE/IRM satellite. It was found that there is a sharp gradient in ion density and ion beta at the interface between the plasma sheet boundary layer and the central plasma sheet. Average flow velocities in the plasma sheet boundary layer were found to be surprisingly low, typically below 100 km/sec.
Published: 01 October 1988
Ultraviolet spectroscopy from the Pioneer Venus Orbiter shows a decline in the cloud top abundance of SO2 from about 100 ppb to about 10 ppb in the period 1978-1986. A consistent decline in polar haze has occurred over the same period, with the correlation coefficient between these two observables of r = 0.8. Star calibrations determine the instrument sensitivity to within 10%, which rules out the possibility that this is an instrumental effect. Systematic errors could increase the SO2 abundance to twice the inferred values in later orbits. Tracking of SO2 features and power spectral analysis give rotation periods for the longer-lived features of 3.6-5.2 days, consistent with cloud-tracked winds observed at other wavelengths. The behavior of SO2 and polar haze can be plausibly explained by episodic injection of SO2 into the cloud top regions, for example, by active volcanism.
Published: 21 May 1988
COS-B viewed the Cyg X-3 region seven times between November, 1975, and February, 1982; a search for steady gamma-ray emission pulsed at the characteristic 4.8-hour period did not reveal its source. Leiden-MIT balloon experiment observations of Cyg X-3 in May, 1979 show the 4.8-hour modulation with sinusoidal light curve and modulation depth of 0.30, for energies of up to about 140 keV. The strong variability of Cyg X-3 over more than one order of magnitude at energies below 20 keV does not emerge in the data collected at hard X-ray energies.
Published: 15 March 1987
The gamma-ray emissions from the Crab pulsar and nebula are analyzed. The data were collected from 1975-1982 in the Galactic anticenter region by COS-B in the energy range 50-3000 MeV. The temporal behavior of the pulsed gamma-ray flux from PSR 0531 + 21 and the unpulsed gamma-ray emissions from the Crab region are examined. It is determined that the spectrum of the pulsar emission is represented by a single power law with an index of 2.00 + or - 0.10 over the energy range of the instrument, and no systematic variation of spectral index with pulsar phase is noted; the spectrum of the unpulsed gamma-ray emission is represented by a single power law with a spectral index of 2.7 + or - 0.3.
Published: 15 March 1987
This is one in a series of papers prepared in association with the release of the final COS-B database. Various aspects of the performance of the COS-B gamma-ray telescope are studied using in-flight data. First, the time-variation of the sensitivity and background over the 6.7 years of the mission is investigated. COS-B observed many regions of the sky repeatedly over the mission lifetime, allowing the study of the temporal behavior of the instrument. Using a multivariate optimization algorithm, the relative sensitivity for the 65 observation periods is determined to an accuracy generally better than 10 percent. The temporal variations of the instrumental background, assumed to be related to a cosmic-ray scaler aboard the satellite, are simultaneously determined. Second, the dependence of the instrumental background on the inclination to the telescope axis is analyzed using observations of high galactic latitude areas. The resulting corrections to the instrumental parameters are a necessary prerequisite for the combination of the data into large-scale maps for scientific analysis. The implementation of the corrections to give such maps is outlined.
Published: 15 January 1987
The cosmic ray (CR) distribution in the Galaxy inside the solar circle is determined by using the kinematics of both H I and CO to ascertain the spatial distribution of the interstellar gas. The conversion factor between integrated CO line intensity and the molecular hydrogen column density is found, and possible large-scale variations of this relationship throughout the Galaxy are investigated. The galactocentric CR distributions are shown to be described satisfactorily by exponential distributions for radii larger than about three, with a radial scale length of 4-11 kpc for electrons and a scale length greater than 18 kpc for nuclei.
Published: 15 January 1986
Pages: 419
Publisher: Biblioteca della Edizioni Scientifiche e Tecniche Mondadori
ISSN: 0303-2752
(Italian)
Published: 01 January 1986
Pages: 133
Publisher: Walker and Company
ISBN: 0-8027-0855-2
Published: 01 January 1985

Editor: Norman Longdon
Scientific Coordinator for ESA SP-1070: Henk Olthof

This report presents the outline of a long term plan for the disciplines of space science falling within the terms of reference of the ESA Directorate of Science. The study, which led to the long term plan proposed in this document, was initiated by the Director of the Scientific Programme in September 1983 and was coordinated by a Survey Committee composed of scientists from different areas of fundamental science.

Contents:

  • Foreword – R.-M. Bonnet, Director of the Scientific Programme
  • Introduction – J. Bleeker, Chairman of the Survey Committee
  • Part 1 – A Long Term Programme for European Space Science
  • Part 2 – Solar System Science
  • Part 3 – Space Astronomy
  • Part 4 – Mission Trends and Industrial Benefits
  • Annex I – Responses to Call for Mission Concepts
  • Annex II – List of Contributors

Published: 01 December 1984
In the present derivation of the radial distribution of high energy gamma-ray emissivity in the outer Milky Way, the kinematics of H I are used to construct column-density maps in various galactocentric distance ranges that are then used in combination with COS-B spacecraft gamma-ray data to determine emissivities in these distance ranges. The results obtained imply a hardening of the gamma-ray spectrum with increasing distance, and include an energy-dependent decrease that is interpreted as a steep gradient in the cosmic-ray electron density and a near constancy of the nuclear component. The galactic origin of electrons with energies of up to several hundreds of MeVs is confirmed.
Published: 16 June 1984
Pulsed gamma-ray emission from radio pulsars has been sought in a study of pulsar parameters for 145 radio observations, contemporary with gamma-ray observations, by the COS-B spacecraft. No signal has been detected in the 50 MeV-2 GeV energy range of the study, either globally or from individual pulsars. These results indicate that the average product of the conversion efficiency from the pulsar braking power into gamma-rays, and the pulsar moment of inertia, cannot exceed 6 x 1043 g cm², for pulsar ages greater than 40,000 years. This implies that the contribution of old pulsars to the observed galactic gamma-ray emission is less than 5 percent for gamma-ray energies greater than 50 MeV.
Published: 15 November 1983
A search through COS-B data for gamma-radiation from a number of extragalactic objects reveals no strong evidence for any positive identification except, as already reported, for the region around the quasar 3C273. Upper limits to the photon fluxes from active extragalactic objects are evaluated using a likelihood method. They reinforce the conclusion reached by Bignami et al. (1979) from the SAS-2 data that the flux upper limits lie substantially below the extrapolation of spectra measured at X-ray energies. The proposed identifications of 2CG135+01 are also discussed
Published: 15 January 1981
5-Jun-2020 10:12 UT

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