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  • 1
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    Ulysses magnetic field observations of fluctuations within polar coronal flows (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Ulysses spacecraft has gathered data from within flows from the Sun's southern polar coronal hole, the first in situ measurement of this region. We present a brief analysis of the heliospheric magnetic field data from this region, using a fractal method. As is the case near the ecliptic, estimated spectral exponents are near 5/3 on spacecraft scales of seconds to minutes. On longer time scales, however, there appears to be a significantly different population in polar flows, which is similar to that found by the Helios spacecraft in fast solar wind flows at 0.3 AU.
    Keywords: ASTROPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 13; 1; p. 105-107
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  • 2
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    The relationship between interplanetary discontinuities and Alfven waves: Ulysses observations (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The rate of occurrence of interplanetary discontinuities (ROID) is examined using Ulysses magnetic field and plasma data from 1 to 5 AU radial distance from the Sun and at high heliographic latitudes. We find two regions where the ROID is high: in stream-stream interaction regions and in Alfven wave trains. This latter feature is particularly obvious at high latitudes when Ulysses enters a high speed stream associated with a polar coronal hole. These streams are characterized by the presence of continuous, large-amplitude (Delta (vector 13)/absolute value of B is about 1-2 Alfven waves and an extraordinarily high ROID value (approximately 150 discontinuities/day). In a number of intervals examined, it is found that (rotational) discontinuities are an integral part of the Alfven waves. The nonlinear Alfven waves are spherically polarized, i.e., the tip of the perturbation vector resides on the surface of a sphere (a consequence of constant absolute value of B). The slowly rotating part of the wave rotates approximately 270 deg in phase. There is a slight arc in the B(sub 1) - B(sub 2) hodogram, suggesting an almost linear polarization. The phase rotation associated with the discontinuity is about 90 deg, lies in the same plane as the slowly rotaing part of the Alfven wave, and therefore completes the 360 deg phase rotation. The best description of the overall Alfven wave plus discontinuity is a spherical, arc-polarized, phase-steepened wave.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 21; p. 2267-2270
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  • 3
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    Spectral polarization analysis of the interplanetary magnetic field fluctuations (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A new computational method and algorithm, based on complex Fourier analysis, is used to derive the spectral density of plane and circularly polarized fluctuation components of the interplanetary magnetic field. Applications of the method have been made using HEOS 2 (1 AU), Pioneer 10 (5 AU), Pioneer 11 (20 AU), and International Cometary Explorer (ICE) (Giocabini-Zinner's comet) data sets. The results show the existence of circularly polarized magnetohydrodynamic (MHD) waves in all cases.
    Keywords: ASTROPHYSICS
    Type: Solar Physics (ISSN 0038-0938); 149; 2; p. 381-389
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  • 4
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    The interplanetary magnetic field from 1 to 5 AU - Ulysses observations (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Observations of the IMF carried out from October 1990 to February 1992 during the in-ecliptic phase of the Ulysses mission are presented. The observations were made between 1 and 5.4 AU during a different phase of the solar cycle from previous missions. The large-scale reorganization of the solar coronal fields following the maximum in Solar Cycle 22 generated numerous transient events, causing large-scale disturbances in interplanetary space, particularly during the first half of 1991. From about the middle of 1991, solar activity apparently decreased, resulting in fewer transient events, allowing the formation of corotating interaction regions (CIRs) recurring in successive solar rotations. Observations of the IMF reflect this temporal evolution in solar activity. However, the average orientation of the IMF, the observed sector structure, and the evolution of the CIRs show that the dynamic interaction of transient events with evolving stream-stream structures in this heliocentric distance range results in significant deviations from the expected IMF topology, even when signature of the transients is less apparent.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 13; 6; p. 15-24.
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  • 5
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    Cometary kilometric radio waves and plasma waves correlated with ion pick-up effect at Comet Halley (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Bow-shock movements at Comet Halley are inferred from the discrete spectra of the cometary kilometric radiation (30-195 kHz); the observed emissions can be interpreted as being generated and propagating from the moving shock. The shock motion is possibly associated with the time variation of the solar wind and cometary outgassing. It is concluded that these plasma wave phenomena are manifestations of ion pick-up processes, which occur even in a remote region 7 million to 10 million km from the cometary nucleus.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 5; 12, 1; 83-88
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  • 6
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    Radial and latitudinal gradients in the interplanetary magnetic field - Evidence for meridional flux transport (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Magnetic field data obtained by the Pioneer 10 and 11 spacecraft in the heliosphere from 1972-1982 and earth orbiting satellite data are examined in terms of radial and latitudinal gradients in the field components and magnitude. The data reveal that higher than expected gradients are observed in the magnetic field and time variations affect the field throughout the low-latitude heliosphere. It is determined that the high radial gradient is caused by meridional flux transport with low-latitude field lines moving to higher heliographic latitudes. High pressure near the solar equator and pressure due to heating in compressive solar wind interaction regions and the large field magnitudes that occur in these regions are investigated as mechanisms that produce the meridional flux. A solar cycle variation in the level of flux transport is analyzed.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 6760-676
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  • 7
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    Discovery of cometary kilometric radiations and plasma waves at Comet Halley (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The plasma-wave probe carried by the spacecraft Sakigake discovered discrete spectra of emissions from Comet Halley in the frequency range 30-195 kHz. The observed cometary kilometric radiation appears to come from moving shocks in the coma region which are possibly associated with temporal variations of the solar wind. Waves due to plasma instabilities associated with the pick-up of cometary ions by the solar wind were observed within a region almost 10 million km from the comet nucleus.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 321; 307-310
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  • 8
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    The bow wave of Comet Giacobini-Zinner - ICE magnetic field observations (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Fitting of a Mach 2 shock surface to the ICE magnetic field data obtained near Comet Giacobini-Zinner has provided subsolar bow wave distances that infer neutral gas outflow rates comparable to previous measurements, and orientations of the bow wave symmetry axis that are consistent with the plasma measurements and motion of the comet relative to the solar wind. Mach values of 1.5-2 and transition thicknesses of the order of 10,000 km are inferred when the field magnitude and variance data are compared. Cross spectra of the transverse field components in and near the bow wave exhibit a peak near 0.01 Hz, or near the cyclotron frequency of ions from the water group. However, the level of turbulence is not consistent with that observed for similar configurations at planetary bow shocks.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 13; 243-246
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  • 9
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    Comet-solar wind interaction - Dynamical length scales and models (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: ICE magnetometer measurements at Comet Giacobini-Zinner and model simulations of comet-solar wind interactions are analyzed. The magnetometer data reveal the existence of intense hydromagnetic turbulence, a draping of the magnetic field lines to form a magnetotail, a weak shock, and a magnetic barrier region in the magnetosphere. The global models of the comet-solar wind interaction are described. The observed data and models are compared and good correlation is displayed.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 13; 239-242
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  • 10
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    Properties of a large-scale interplanetary loop structure as deduced from low-energy proton anisotropy and magnetic field measurements (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Correlated particle and magnetic field measurements by the ISEE 3 spacecraft are presented for the loop structure behind the interplanetary traveling shock event of Nov. 12, 1978. Following the passage of the turbulent shock region, strong bidirectional streaming of low-energy protons is observed for approximately 6 hours, corresponding to a loop thickness of about 0.07 AU. This region is also characterized by a low relative variance of the magnetic field, a depressed proton intensity, and a reduction in the magnetic power spectral density. Using quasi-linear theory applied to a slab model, a value of 3 AU is derived for the mean free path during the passage of the closed loop. It is inferred from this observation that the proton regime associated with the loop structure is experiencing scatter-free transport and that either the length of the loop is approximately 3 AU between the sun and the earth or else the protons are being reflected at both ends of a smaller loop.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 6-14
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