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  • 1995-1999  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 17 (1999), S. 639-641 
    ISSN: 0992-7689
    Keywords: Solar physics ; astrophysics and astronomy (magnetic fields; general)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Using the annual number of geomagnetically quiet days (aa 〈 20 γ) for the year after the solar minimum, this precursor method predicts that the maximum sunspot number for cycle 23 will be 140 + 32, indicating that cycle 23 will be similar to cycles 21 and 22.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 15 (1997), S. 397-402 
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Following a given classification of geomagnetic activity, we obtained aa index values for the Maunder minimum (1645–1715). It is found that the recurrent and fluctuating activities were not appreciable and that the shock activity levels were very low. The aa index level was due almost entirely to the quiet days. Calculated average solar-wind velocities were 194.3 km s−1 from 1657 to 1700 and 218.7 km s−1 from 1700 onwards. Also, the coronal magnetic field magnitude and southward interplanetary magnetic field component Bz were lower. It is concluded that the nearly absent levels of geomagnetic activity during this period were due to lower coronal and Bz magnetic field magnitudes as well as to the continuous impinging on the Earth of a slow wind.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 185 (1999), S. 405-416 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We analyse data of magnetic flux emergence for solar cycles 21 and 22, Helios 1 interplanetary shocks for cycle 21, and sudden storm commencements (SSCs) for cycles 11–22. A dominant variation of 3-year periodicity was found for all three phenomena during cycles 21 and 22. This indicates a correlation and a possible influence of the rate of solar magnetic flux emergence to produce the interplanetary phenomena studied in this work; in particular, the suggested role of coronal mass ejections as a means by which magnetic flux and stresses are taken out of the corona seems to be plausible. When taking cycles 11–22 in SSCs, the main periodicity changes to around 4 years; this may be an indication of flux emergence rate variations over the cycles.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is widely accepted now that a significant fraction of the solar energetic particles (SEPs) observed at 1 AU after major solar flares are actually accelerated at a CME-driven shock. In addition, in the emerging new paradigm for SEP acceleration in different sources at or near the Sun, the existence of two types of flares – impulsive and gradual – is recognized. Within this concept, it is tempting also to separate SEPs into two groups – interacting and escaping – and to derive their 'source spectra' from observational data on various flare emissions (protons, gamma rays, neutrons, etc.). By different techniques, those spectra have been reconstructed for 80 solar proton events (SPE) in 1949–1991. In this paper, all available data on the source spectra of solar protons are summarized and revised. We discuss in detail existing uncertainties in the derived spectral indexes, consider other methodological problems involved in this study, and suggest several possible lines for the future investigations of solar flares and SCRs using the source spectrum data. It is noted that some peculiarities of the spectra, for instance, spectral steepening for high energies, may be characteristic of large events of the 23 February 1956 type.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 160 (1995), S. 353-362 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examined solar energetic proton (SEP) events associated with intense Hα flares. We located these flares on the solar disk and obtained their distribution in heliographic longitude as well as their angular distance distribution with respect to the neutral lines corresponding to the heliospheric current sheet at 2.5R⊙. We found that the SEP-associated Hα flares tend to occur in active regions at the feet of those helmet streamers which form the heliomagnetic equator and are related to coronal mass ejections (CMEs) and CME shocks. We discuss the possible role of flares, CMEs and CME shocks in generating SEPs.
    Type of Medium: Electronic Resource
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