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  • 1
    Electronic Resource
    Electronic Resource
    Energetic neutral atoms from a trans-Europa gas torus at Jupiter (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 421 (2003), S. 920-922 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The space environments—or magnetospheres—of magnetized planets emit copious quantities of energetic neutral atoms (ENAs) at energies between tens of electron volts to hundreds of kiloelectron volts (keV). These energetic atoms result from charge exchange between magnetically trapped ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01431
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Large-scale structure of the interplanetary medium (1973)
    Springer
    Solar physics 33 (1973), S. 483-504 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We introduce a method for constructing large-scale (∼0.25 AU) interplanetary magnetic field lines using only solar wind velocity from well-separated appropriately located spacecraft. The technique is based on ‘labeling’ the field lines at each spacecraft with their coronal connection longitudes calculated in the EQRH (extrapolated quasi-radial hypervelocity) approximation (Nolte and Roelof, 1973). Even though the EQRH approximation is most applicable to quasi-steady solar wind, we propose that it should also be satisfactorily accurate for moderately evolving conditions. For strongly evolving conditions (e.g., flare-associated plasma) we propose a straightforward correction based on the inferred coronal longitudinal velocity profile. To illustrate the multispacecraft EQRH technique, we perform a calculation in which the interplanetary field lines in a model evolving solar wind disturbance are deduced from model observations at separated spacecraft. Since the expected agreement is found, we use data from Pioneers 8 and 9 and Vela to construct field lines for an unusually quiet period (April 26–30, 1969) and for a flare-associated disturbance accompanied by a Forbush decrease (March 23–25, 1969). The deduced field lines (even though strongly distorted by the disturbance), order the onsets of the Forbush decrease at the separated spacecraft, and the interplanetary plasma and field structures correspond to equatorial structures apparent in Hα synoptic charts of chromospheric magnetic features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152435
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  • 4
    Electronic Resource
    Electronic Resource
    Coronal holes as sources of solar wind (1976)
    Springer
    Solar physics 46 (1976), S. 303-322 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the association of high-speed solar wind with coronal holes during the Skylab mission by: (1) direct comparison of solar wind and coronal X-ray data; (2) comparison of near-equatorial coronal hole area with maximum solar wind velocity in the associated streams; and (3) examination of the correlation between solar and interplanetary magnetic polarities. We find that all large near-equatorial coronal holes seen during the Skylab period were associated with high-velocity solar wind streams observed at 1 AU.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149859
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  • 5
    Electronic Resource
    Electronic Resource
    High coronal structure of high velocity solar wind stream sources (1977)
    Springer
    Solar physics 51 (1977), S. 459-471 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract When solar wind plasma in the trailing (eastern) edge of a high-speed stream is mapped back to its estimated source in the high corona using the constant radial velocity (EQRH) approximation, a large range of velocities appears to come from a restricted range in longitude, often only a few degrees. This actually constitutes a sharp eastern coronal boundary for the solar wind stream source, and demands that the boundary have a three-dimensional structure. Using interplanetary data, we infer a systematic variation in ‘source altitude’ (identified approximately with the Alfvén point), with faster solar wind attaining its interplanetary characteristics at lower altitudes. This also affects the accuracy of the source longitude estimates, so that we infer a width in the high corona of 4–6° for the source of the trailing edges of streams which appear to originate from a single longitude. We demonstrate that the possible systematic interplanetary effects (in at least some cases) are not large (≲ 2° in heliocentric longitude). The relatively sharp boundaries imply that high-speed streams are well-defined structures all the way down to their low coronal sources, and that the magnetic field structure controls the propagation of the plasma through the corona out to the vicinity of the Alfvén point (≳ 20 R ⊙).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216379
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  • 6
    Electronic Resource
    Electronic Resource
    Co-rotating particle enhancements out of the ecliptic plane (1995)
    Springer
    Space science reviews 72 (1995), S. 327-330 
    Details
    ISSN: 1572-9672
    Keywords: Heliosphere ; Energetic particles ; co-rotating interaction regions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The characteristics of the recurrent electron (38–53 keV) and ion (〉∼0.5 MeV) enhancements observed by Ulysses from mid-1992 to April 1994 are presented. The magnitude of the ion flux increases reached a maximum at a latitude of ∼20°S and decreased afterwards by ∼23%/degree until early 1994. The magnitude of the electron increases showed a similar trend until May, 1993, after which time it became approximately constant, until it started to increase again in early 1994. The electron enhancements have lagged the protons by up to 5 days once Ulysses left the heliospheric current sheet (mid-1993). The electron spectral index tended to harden (a) during the decay of the event and (b) as the latitude increased, up to 50°S. The events have recurred on a 26.0 day period, but with significant phase shifts over the 25 rotations studied. The H/He ratio decreases across the maximum intensity. The mean minimum value for H/He was 3.5±0.3, lower than that measured in previous studies in the ecliptic plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768799
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Reverse shock acceleration of electrons and protons at mid-heliolatitudes from 5.3-3.8 AU (1995)
    Springer
    Space science reviews 72 (1995), S. 303-308 
    Details
    ISSN: 1572-9672
    Keywords: Heliosphere ; Energetic particles ; Shock acceleration ; Reverse shocks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examine the intensity, anisotropy and energy spectrum of 480–966 keV protons and 38–315 keV electrons observed by the HI-SCALE instrument on Ulysses associated with Corotating Interaction Regions (CIR) from mid-1992 to early 1994. The particle events are most clearly ordered by the reverse shocks bounding the CIRs. The bulk of the ion fluxes appear either straddling, or with their maximum intensity following, the reverse shock. The electron intensities rise sharply to their maximum upon the passage of the reverse shock, and are delayed with respect to the protons. We believe that following acceleration at the reverse shock the electrons re-enter the inner heliosphere and mirror, to return to the reverse shock for repeated acceleration. This process is more effective for electrons (v∼c/2) than for ions, and also favours the higher velocity electrons, which accounts for the observed spectral hardening with latitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768795
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  • 9
    Electronic Resource
    Electronic Resource
    Large-scale structure of the interplanetary medium (1973)
    Springer
    Solar physics 33 (1973), S. 241-257 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We propose that the coronal source longitude and latitude of solar wind plasma can be estimated within ∼ 10°. Previous writers have argued that the solar wind in the ecliptic should originate near the equator and that a quasi-radial hypervelocity (QRH) approximation (constant radial flow) is valid beyond the magnetohydrodynamic critical points. We demonstrate that an extension of the QRH approximation (as if the solar wind flowed radially with constant velocity from the center of the Sun) yields a proper estimate of the high coronal source location at the ‘release zone’ where the solar wind makes its transition to radial interplanetary flow. This ‘extrapolated’ QRH (or EQRH) approximation succeeds because the two main corrections to this source estimate, coronal corotation and interplanetary acceleration, tend to cancel (the former correcting the source location eastward, the latter westward). Although this ‘ideal spiral’ approximation was first suggested by Snyder and Neugebauer (1966), only recently has it been demonstrated that it relates a wide range of interplanetary plasma, magnetic field and energetic particle data to observed coronal magnetic structure. We estimate quantitatively the error in the EQRH approximation by comparison with steady-state streamlines predicted by azimuthally independent and dependent theoretical solutions to the steady-state plasma equations. We find the error in both cases ⩽ 10° in longitude and therefore suggest that the EQRH approximation offers the means to relate observed solar ‘initial conditions’ in the ‘release zone’ directly to interplanetary measurements. If, in addition, the EQRH approximation also leads to agreement with low coronal structure, then there should be a straightforward correspondence to otherwise unobservable high coronal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152395
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  • 10
    Electronic Resource
    Electronic Resource
    A coronal hole and its identification as the source of a high velocity solar wind stream (1973)
    Springer
    Solar physics 29 (1973), S. 505-525 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract X-ray images of the solar corona, taken on November 24, 1970, showed a magnetically open structure in the low corona which extended from N20W20 to the south pole. Analysis of the measured X-ray intensities shows the density scale height within the structure to be typically a factor of two less than that in the surrounding large scale magnetically closed regions. The structure is identified as a coronal hole. Since there have been several predictions that such a region should be the source of a high velocity stream in the solar wind, wind measurements for the appropriate period were traced back to the Sun by the method of instantaneous ideal spirals. A striking agreement was found between the Carrington longitude of the solar source of a recurrent high velocity solar wind stream and the position of the hole. Solar wind bulk velocity and photospheric magnetic field data from the period 1962–1970 indicate the possible extension of the result to the interpretation of long term variations in the wind pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150828
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