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  • 1
    Electronic Resource
    Electronic Resource
    Enhanced low-energy gamma rays at balloon altitude in the Brazilian magnetic anomaly (1974)
    [s.l.] : Nature Publishing Group
    Nature 252 (1974), S. 25-27 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] As a part of the continuing cosmic ray programme at INPE, balloons with ?-ray and charged particle detectors were launched on October 7 and 20, 1973. They reached the ceiling altitude of ?3.5 mbar and remained there for few hours measuring ?-ray and charged particle fluxes. The magnetograms ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/252025a0
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  • 2
    Electronic Resource
    Electronic Resource
    Low-energy proton increases associated with interplanetary shock waves (1971)
    Springer
    Solar physics 21 (1971), S. 204-224 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Impulsive increases in the low energy proton flux observed by the Explorer 34 satellite, in very close time association with geomagnetic storm sudden commencements are described. It is shown that these events are of short duration (20–30 min) and occur only during the decay phase of a solar cosmic-ray flare event. The differential energy spectrum and the angular distribution of the direction of arrival of the particles are discussed. Two similar increases observed far away from the earth by the Pioneer 7 and 8 deep-space probes are also presented. These impulsive increases are compared with Energetic Storm Particle events and their similarities and differences are discussed. A model is suggested to explain these increases, based on the sweeping and trapping of low energy cosmic rays of solar origin by the advancing shock front responsible for the sudden commencement detected on the Earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155791
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for confinement of low-energy cosmic rays ahead of interplanetary shock waves (1973)
    Springer
    Solar physics 30 (1973), S. 243-253 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Short-lived (∼ 15 min), low-energy proton increases associated with the passage of interplanetary shock waves have been previously reported. In the present paper, we have examined in a fine time scale (∼ 1 min) the concurrent particle and magnetic field data, taken by detectors on Explorer 34, for four of these events which occurred on 30 May 1967, 5 June 1967, 29 November 1967, and 11 January 1968. Our results further support the view that these impulsive events are due to confinement of the solar cosmic-ray particles in the region just ahead (∼ 106 km) of the advancing shock front. Data from the Pioneer 7 spacecraft for a similar event on 30 August 1966, when this spacecraft was 1.9 × 106 km from the Earth, are shown to be consistent with this interpretation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156193
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  • 4
    Electronic Resource
    Electronic Resource
    The small anisotropy and the rigidity spectrum of the March 30, 1969 solar flare event (1970)
    Springer
    Solar physics 14 (1970), S. 419-426 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study of the March 30, 1969 solar flare event is presented utilizing data obtained from the world-wide network of neutron monitors. Although, to a good first approximation, the solar flare radiation displayed a high degree of isotropy at the orbit of the earth, it is deduced that a small anisotropy from East of the earth-sun line was present at the time of maximum enhancement of the event. This small deduced anisotropy does not, however, preclude the use of a method, based on isotropic particle propagation, to calculate the rigidity spectral index of the flare-induced radiation. Use of such a method determines the differential rigidity spectral index to be 3.9 ± 0.1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221328
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  • 5
    Electronic Resource
    Electronic Resource
    Neutron monitor and Pioneer 6 and 7 studies of the January 28, 1967 solar flare event (1969)
    Springer
    Solar physics 10 (1969), S. 198-211 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A discussion of the January 28, 1967 solar flare event is presented. High energy data from several neutron monitor stations are supplemented by low energy data from the interplanetary space probes Pioneers 6 and 7. A study of the data obtained from these three observation stations widely separated in solar azimuth has shown (1) the most probable location for the responsible flare was ≈ 60 ° beyond the western solar limb, (2) other than the large emitted particle flux, the phenomena associated with the January 28 activity are not atypical of other solar flare effects, (3) both the ≳ 0.5 GeV and ≳ 7.5 MeV fluxes observed at the earth were isotropic, indicative of particle diffusion across the interplanetary magnetic field lines, (4) the spectral exponent of the differential rigidity spectrum at high energies was - 4.8 ± 0.2, and (5) there was an indication of low energy solar injection prior to the high energy event of January 28. A technique is also described for obtaining the differential rigidity spectral index for an isotropic flux as a function of the relative enhancements of any pair of neutron monitors sufficiently separated in latitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146170
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  • 6
    Electronic Resource
    Electronic Resource
    The degree of anisotropy of cosmic ray electrons of solar origin (1971)
    Springer
    Solar physics 17 (1971), S. 241-268 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Data obtained by the Explorer 34 satellite regarding the degree of anisotropy of ≳ 70 keV electrons of solar origin are reported. It is shown that the anisotropies are initially field aligned, and that they decay to ≲ 10% in a time of the order of 1 hr. The decays of the concurrent ionic and electronic anisotropies for one well observed event are in good agreement with the diffusive propagation model of Fisk and Axford. The data suggest parallel diffusion coefficients for both ions and electrons that are rigidity independent. From considerations of a long lived electron event, it is shown that the electronic fluxes exhibit ‘equilibrium’ anositropies at late times. These are interpreted as indicating that convective removal at the solar wind velocity is the dominant mechanism whereby solar cosmic ray electrons (∼- 70 keV) leave the solar system. They also indicate that there is a positive density gradient at late times in a solar electron event. The data suggest that this was established prior to the establishment of a similar gradient for the cosmic ray ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152875
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  • 7
    Electronic Resource
    Electronic Resource
    Anisotropy characteristics of low energy cosmic ray population of solar origin (1971)
    Springer
    Solar physics 19 (1971), S. 209-233 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Comparison of Explorer 34 observations on solar protons in the energy range 0.7–55 MeV with similar observations from other spacecrafts show that the large field aligned anisotropies which are observed during the rise time of a flare event change to an equilibrium anisotropy coming radially from the sunward direction due to the convective removal of the solar particles. At very late times during the decay (T ⩾ 4 days) the anisotropy is observed to be from a direction ∼ 45° E of the satellite-Sun line which is interpreted as indicative of positive density gradient of solar cosmic ray population. The dependence of both types of equilibrium anisotropies on the energy and the velocity of the particles and on plasma velocity are shown to be in agreement with the theoretical predictions. The amplitude of the large field aligned anisotropies observed earlier in the event is found to be independent of the rise time of the event and to vary as (Vt)−1. Interplanetary magnetic sector crossings during a flare event, cause abrupt changes in both the amplitude and phase of the non-equilibrium anisotropy whereas they have no significant effect on equilibrium anisotropy. The effect of azimuthal density gradients on the decay time constants of flare enhancements are also examined in an attempt to understand the complicated structures, often observed, in the time intensity profiles at low energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148836
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  • 8
    Electronic Resource
    Electronic Resource
    An instrument to measure anisotropies of cosmic ray electrons and protons for the explorer 34 satellite (1971)
    Springer
    Solar physics 17 (1971), S. 218-240 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An instrument to measure the anisotropy and energy spectra of cosmic-ray electrons and protons, and X-rays of solar and galactic origin is described. Such instruments were launched on 24 May, 1967 and 21 June, 1969 as component parts of the scientific payloads of the Explorer 34 and 41 satellites. A general description and the main characteristics of the detectors are presented and the stability of the instrument on Explorer 34 over its 23 months of operation is discussed. The method of analysis of the obtained angular distribution of solar cosmic ray particles in the ecliptic plane is given. It is shown that the anisotropy of low energy particles of solar origin decreases sharply to a very small value when the satellite penetrates the magnetosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152874
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  • 9
    Electronic Resource
    Electronic Resource
    Cosmic ray anisotropies observed late in the decay phase of solar flare events (1974)
    Springer
    Solar physics 38 (1974), S. 227-256 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Concurrent interplanetary magnetic field and 0.7–7.6 MeV proton cosmic-ray anisotropy data obtained from instrumentation on Explorers 34 and 41 are examined for five cosmic-ray events in which we observe a persistent eastern-anisotropy phase late in the event (t ≳ 4 days). The direction of the anisotropy at such times shows remarkable invariance with respect to the direction of the magnetic field (which generally varies throughout the event) and it is also independent of particle species (electrons and protons) and particle speed over the range 0.06 ⩽ β ⩽ 0.56. The anisotropy is from the direction 38.3° ± 2.4° E of the solar radius vector, and is inferred to be orthogonal to the long term, mean interplanetary field direction. Both the amplitude of the anisotropy and the decay time constant show a strong dependence on the magnetic field azimuth. Detailed comparison of the anisotropy and the magnetic field data shows that the simple model of convection plus diffusion parallel to the magnetic field is applicable for this phase of the flare effect. It is demonstrated that contemporary theories do not predict the invariance of the direction as observed, even when the magnetic field is steady; these theories need extension to take into account the magnetic field direction ψ varying from its mean direction ψ o. It is shown that the late phase anisotropy vector is not expected to be everywhere perpendicular to the mean magnetic field. The suggestion that we are observing kinks in the magnetic field moving radially outwards from the Sun leads to the conclusion that the parallel diffusion coefficient varies as 1/cos2 (ψ − ψ o). Density gradients in the late decay phase are estimated to be ≈ 700%∣AU for 0.7–7.6 MeV protons. A simple theory reproduces the dependence of the decay time constant on anisotropy; it also leads to a radial density gradient of about 1000%∣AU and diffusion coefficient of 1.3 × 1020 cm2 s−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00161840
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  • 10
    Electronic Resource
    Electronic Resource
    Monte Carlo model of the highly anisotropic solar proton event of 20 April 1971 (1975)
    Springer
    Solar physics 40 (1975), S. 449-460 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The anisotropy of the particle distribution and its variation with time at 1 AU early in a solar cosmic ray event can provide information on the pitch-angle scattering of the particles in the interplanetary medium. The proton event of 20 April 1971 is described in which the anisotropy of the 7.6–55 MeV energy channel remained large (≳ 100%) and field-aligned well into the decay phase of the event. A Monte Carlo technique, which gives the pitch-angle distribution, is employed to investigate two models put forward to explain this sustained anisotropy. It is shown that the observed event is consistent with one model in which the injection of particles at the Sun decayed with ane-folding time of 7 hr. In this model the parallel propagation is determined by small-angle scattering in a diverging field equivalent to a uniform diffusion coefficient of 2.1 × 1022 cm2 s−1 (the corresponding classical mean free path is 0.90 AU). A model with impulsive injection and in whichκ(r) increases strongly with distance from the Sun cannot satisfactorily explain the observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00162391
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