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  • 1
    Electronic Resource
    Electronic Resource
    Voyager 1 exited the solar wind at a distance of ∼85  au from the Sun (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 426 (2003), S. 45-48 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The outer limit of the Solar System is often considered to be at the distance from the Sun where the solar wind changes from supersonic to subsonic flow. Theory predicts that a termination shock marks this boundary, with locations ranging from a few to over 100 au ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02068
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  • 2
    Electronic Resource
    Electronic Resource
    Numerical simulation of positive-potential conductors in the presence of a plasma and a secondary-emitting dielectric (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4991-4995 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 2 (1)/(2) -dimensional, cylindrically symmetric particle in cell program is used to simulate the interaction of a plasma with a positively biased disk covered by a dielectric material (Kapton). Several runs using different combinations of bias voltages and secondary electron yields are discussed. Special attention is paid to the role of the secondaries as the dielectric surface changes from a negative potential to become increasingly positive. This is termed the "snapover'' process. The contribution due to secondaries is examined by plotting the distribution (number versus position) of the particles emitted by the impacting on the dielectric. These plots show that secondaries are drawn back into the dielectric as well as the conductor in the case of snapover. Mechanisms and experimental implications for these particular distributions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335500
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  • 3
    Electronic Resource
    Electronic Resource
    An investigation on grain equilibrium potential in a plasma environment (1984)
    Springer
    Astrophysics and space science 102 (1984), S. 179-188 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The charging of solid grains in a plasma environment is considered in this study. It is found that grains with zero initial potential gradually gain a negative potential and approach equilibrium. This potential depends most strongly on the plasma temperature. If secondary and photoemission of electrons from this grain is not considered, this equilibrium potential is about −2.7 times the plasma thermal energy. If secondary and photoemission is included, the grain can approach equilibrium at positive rather than negative potential. In this case the sign and the value of the equilibrium potential depends strongly on the material properties and to lesser extent on plasma temperature. This implies that grains of different composition can have different, possibly even opposite, equilibrium potentials in the same plasma environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651070
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  • 4
    Electronic Resource
    Electronic Resource
    IMF connection for energetic protons observed at Ulysses via mid-latitude solar wind rarefaction regions (1995)
    Springer
    Space science reviews 72 (1995), S. 309-314 
    Details
    ISSN: 1572-9672
    Keywords: Heliosphere ; Energetic particles ; Corotating high-speed streams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As Ulysses moved inward and southward from mid-1992 to early 1994 we noticed the occasional occurrence of “inter-events”, lasting about 10 days and falling between the recurrent events, observed at proton energies of 0.48–97 MeV, associated with Corotating Interaction Regions (CIR). These inter-events were present for several sequences of two or more solar rotations at intensity levels around 1% of those of the neighbouring main events. When we compared the Ulysses events with those measured on IMP-8 at 1 AU we saw that the inter-events appeared at Ulysses after the extended emission (〉10 days) of large fluxes of solar protons of the same energy that lasted at least one solar rotation at 1 AU. The inter-events fell completely within the rarefaction regions (dv/dt〈0) of the recurrent solar wind streams. The interplanetary magnetic field (IMF) lines in the rarefactions map back to the narrow range of longitudes at the Sun which mark the eastern edge of the source region of the high speed stream. Thus the inter-events are propagating at mid-latitudes to Ulysses along field lines free from stream-stream interactions. They are seen in the 0.39–1.28 MeV/nucleon He, which exhibit a faster decay, but almost never in the 38–53 keV electrons. We show that the inter-events are unlikely to be accelerated by reverse shocks associated with the CIRs and that they are more likely to be accelerated by sequences of solar events and transported along the IMF in the rarefactions of the solar wind streams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768796
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  • 5
    Electronic Resource
    Electronic Resource
    Solar proton events during solar cycles 19, 20, and 21 (1990)
    Springer
    Solar physics 126 (1990), S. 385-401 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Solar proton events have been studied for over thirty years and a great deal of lore has grown around them. It is the purpose of this paper to test some of this lore against the actual data. Data on solar proton events now exist for the period from 1956 to 1985 during which time 140 events took place in which the event integrated fluxes for protons of energy 〉 30 MeV was larger than 105 particles cm-2. We have studied statistical properties of event integrated fluxes for particles with energy 〉 10 MeV and for particles with energy 〉 30 MeV. Earlier studies based on a single solar cycle had resulted in a sharp division of events into ‘ordinary’ and ‘anomalously large’ events.Two such entirely separate distributions imply two entirely separate acceleration mechanisms, one common and the other very rare. We find that the sharp division is neither required nor justified by this larger sample. Instead the event intensity forms a smooth distribution for intensities up to the largest observed implying that any second acceleration mechanism cannot be rare. We have also studied the relation of event sizes to the sunspot number and the solar cycle phase. We find a clear bimodal variation of annual integrated flux with solar cycle phase but no statistically significant tendency for the large events to avoid sunspot maximum. We show there is almost no relation between the maximum sunspot number in a solar cycle and the solar cycle integrated flux. We also find that for annual sunspot numbers greater than 35 (i.e., non-minimum solar cycle conditions) there is no relation whatsoever between the annual sunspot numbers and annual integrated flux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00153058
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  • 6
    Electronic Resource
    Electronic Resource
    Electromagnetic and corpuscular emission from the solar flare of 1991 June 15: Continuous acceleraton of relativistic particles (1994)
    Springer
    Solar physics 150 (1994), S. 267-283 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Data on X-,γ-ray, optical and radio emission from the 1991 June 15 solar flare are considered. We have calculated the spectrum of protons that producesγ-rays during the gradual phase of the flare. The primary proton spectrum can be described as a Bessel-function-type up to 0.8 GeV and a power law with the spectral index ≈3 from 0.8 up to 10 GeV or above. We have also analyzed data on energetic particles near the Earth. Their spectrum differed from that of primary protons producingγ-ray line emission. In the gradual phase of the flare additional pulses of energy release occurred and the time profiles of cm-radio emission andγ-rays in the 0.8–10 MeV energy band and above 50 MeV coincided. A continuous and simultaneous stochastic acceleration of the protons and relativistic electrons at the gradual phase of the flare is considered as a natural explanation of the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712889
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of temporal and spatial variations in the Fe/O charge composition of the solar particle event of 4 July, 1974 (1976)
    Springer
    Solar physics 49 (1976), S. 395-407 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Comprehensive measurements of the temporal variations of the Z ≥ 6 charge composition in the 4 July 1974 solar event made with experiments aboard IMP-7 and 8 show that large variations in the charge composition occur in three-hour-averaged intensities. Hourly averaged fluxes show variations as large as factors of 3 to 4 from one hour to the next and 3 hour averages show nearly a factor of 10 peak to minimum over the event. The precision of the measurements are limited by counting statistics of the Fe-group channel. Iron to oxygen variations are established by both rate channel and pulse height analysis techniques. Comparison of measurements from IMP-7 and 8, separated by about 70 R E shows that, while significant differences in composition and intensity exist for brief periods, the gross compositional variations are reproduced well at both spacecraft. These observations provide particularly stringent conditions for theories of the acceleration, release, and propagation of solar energetic particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00162460
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  • 8
    Electronic Resource
    Electronic Resource
    Ulysses observations of a coronal origin particle event at 32° south heliographic latitutde (1995)
    Springer
    Space science reviews 72 (1995), S. 315-320 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A remarkable streaming beam-like particle event of 60 keV-5 MeV ions and of 38–315 keV electrons has been reported previously. This event has been associated with the passage of a Coronal Mass Ejection (CME) over the Ulysses spacecraft on June 9–13, 1993. At this time, the spacecraft was located at 4.6 AU from the sun and at an heliolatitude of 32° south. It was proposed (Armstrong et al., 1994) that the particle injection source could have been of coronal origin. In this study, we analyse the solar activity during this period. We identify a region of solar radio noise storms in the corona and in particular, a flare on June 7 that presents all the required characteristics to produce the hot plasma beam observed in the interplanetary medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768797
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  • 9
    Electronic Resource
    Electronic Resource
    The acceleration of charged particles in interplanetary shock waves (1982)
    Springer
    Space science reviews 32 (1982), S. 185-204 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The theory and observations of energetic ion acceleration in interplanetary shock waves is reviewed. The shock acceleration of the solar wind plasma and particle transport effects are discussed. Suggestions are offered for future research in shock acceleration physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225184
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  • 10
    Electronic Resource
    Electronic Resource
    The Low Energy Charged Particle (LECP) experiment on the Voyager spacecraft (1977)
    Springer
    Space science reviews 21 (1977), S. 329-354 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Low Energy Charged Particle (LECP) experiment on the Voyager spacecraft is designed to provide comprehensive measurements of energetic particles in the Jovian, Saturnian, Uranian and interplanetary environments. These measurements will be used in establishing the morphology of the magnetospheres of Saturn and Uranus, including bow shock, magnetosheath, magnetotail, trapped radiation, and satellite-energetic particle interactions. The experiment consists of two subsystems, the Low Energy Magnetospheric Particle Analyzer (LEMPA) whose design is optimized for magnetospheric measurements, and the Low Energy Particle Telescope (LEPT) whose design is optimized for measurements in the distant magnetosphere and the interplanetary medium. The LEMPA covers the energy range from ∼10 keV to 〉 11 MeV for electrons and from ∼15 keV to ≳ 150 MeV for protons and heavier ions. The dynamic range is ∼0.1 to ≳ 1011 cm−2 sec−1 sr−1 overall, and extends to 1013 cm−2 sec−1 sr−1 in a current mode operation for some of the sensors. The LEPT covers the range ∼0.05 ≤ E ≳ 40 MeV/nucleon with good energy and species resolution, including separation of isotopes over a smaller energy range. Multi-dE/dx measurements extend the energy and species coverage to 300–500 MeV/nucleon but with reduced energy and species resolution. The LEPT employs a set of solid state detectors ranging in thickness from 2 to ∼2450 μ, and an arrangement of eight rectangular solid state detectors in an anticoincidence cup. Both subsystems are mounted on a stepping platform which rotates through eight angular sectors with rates ranging from 1 revolution per 48 min to 1 revolution per 48 sec. A ‘dome’ arrangement mounted on LEMPA allows acquisition of angular distribution data in the third dimension at low energies. The data system contains sixty-two 24-bit sealers accepting data from 88 separate channels with near 100% duty cycle, a redundant 256-channel pulse height analyzer (PHA), a priority system for selecting unique LEPT events for PHA analysis, a command and control system, and a fully redundant interface with the spacecraft. Other unique features of the LECP include logarithmic amplifiers, particle identifiers, fast (∼15 ns FWHM) pulse circuitry for some subsystems, inflight electronic and source calibration and several possible data modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211545
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