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  • 1
    Electronic Resource
    Electronic Resource
    The geomagnetic response to the Earth's crossing of the heliospheric current sheet
    Amsterdam : Elsevier
    Advances in Space Research 13 (1993), S. 41-44 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(93)90310-8
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  • 2
    Electronic Resource
    Electronic Resource
    The association of Coronal Mass Ejections during solar maximum times with the heliomagnetic current sheet
    Amsterdam : Elsevier
    Advances in Space Research 13 (1993), S. 183-186 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(93)90475-Q
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  • 3
    Electronic Resource
    Electronic Resource
    Microwave and Soft X-ray Study of Solar Active Region Evolution (1998)
    Springer
    Solar physics 178 (1998), S. 353-378 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the properties and evolution of several active regions observed at multiple wavelengths over a period of about 10 days. We have used simultaneous microwave (1.5 and 17 GHz) and soft X-ray measurements made with the Very Large Array (VLA), the Nobeyama Radio Heliograph (NRH) and the Soft X-ray Telescope (SXT) on board the Yohkoh spacecraft, as well as photospheric magnetograms from KPNO. This is the first detailed comparison between observations at radio wavelengths differing by one order of magnitude. We have performed morphological and quantitative studies of active region properties by making inter-comparison between observations at different wavelengths and tracking the day-to-day variations. We have found good general agreement between the 1.5 and 17 GHz radio maps and the soft X-rays images. The 17 GHz emission is consistent with thermal bremsstrahlung (free-free) emission from electrons at coronal temperatures plus a small component coming from plasma at lower temperatures. We did not find any systematic limb darkening of the microwave emission from active regions. We discuss the difference between the observed microwave brightness temperature and the one expected from X-ray data and in terms of emission of a low temperature plasma at the transition region level. We found a coronal optical thickness of ∼ 10-3 and ∼ 1 for radiation at 17 and 1.5 GHz, respectively. We have also estimated the typical coronal values of emission measure (∼ 5 × 1028 cm-5), electron temperature (∼ 4.5 × 1066 K) and density (∼ 1.2 × 109 cm3). Assuming that the emission mechanism at 17 GHz is due to thermal free-free emission, we calculated the magnetic field in the source region using the observed degree of polarization. From the degree of polarization, we infer that the 17 GHz radiation is confined to the low-lying inner loop system of the active region. We also extrapolated the photospheric magnetic field distribution to the coronal level and found it to be in good agreement with the coronal magnetic field distribution obtained from microwave observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004982902622
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  • 4
    Electronic Resource
    Electronic Resource
    Frequency distributions of solar gamma ray events related and not related with spes in 1980–1995 (1999)
    Springer
    Solar physics 188 (1999), S. 169-185 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The advent of new and better instruments in space has resulted in a considerable increase in the number of solar gamma-ray events (GRE) detected. In this paper, we analyze available SMM/GRS and GRANAT/PHEBUS data on the hard X-ray and gamma-ray events, and their associations with solar proton events (SPE) at the Earth's orbit, for the observation period of 1980–1995. About 58% of the GREs under study were found to be SPE-related ones. Size (frequency) distributions have been obtained, for the first time, for the events with different types of emissions (bremsstrahlung, narrow GR lines, positron annihilation line, neutron capture line, SPEs, etc.). We discuss the possible relationships between size distributions implied by the parameter correlation. The distribution for GR events turns out to be generally harder than that for X-ray bursts. The GREs involving energetic particles in space are shown to have a harder frequency distribution in comparison with that for GREs without detectable SPEs. There is also a tendency for the GREs with highest fluences to be related with SPEs. Finally, no correlation seems to exist between the GRL fluence and maximum flux of 〉10 MeV protons near the Earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005190331163
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  • 5
    Electronic Resource
    Electronic Resource
    On the role of energetic particles in solar flares (1985)
    Springer
    Solar physics 97 (1985), S. 131-144 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The importance of energetic particles in the generation of solar flares and related phenomena has been underestimated if not completely neglected. A reexamination of their role in the light of recent observations carried out during the last solar maximum by a number of experiments on SMM and Hinotori satellites points out the continuous and violent evolution of the solar atmosphere. Most observed features can be better explained by the old idea that particles are trapped in magnetic loops above active regions where they are first heated and then accelerated by absorbing part of the wave energy flowing upwards continuously from the convection zone. Their catastrophic release into the chromosphere as a consequence of an instability in the region such as chromospheric heating or due to the emergence of new magnetic flux is considered as being the flare proper. Since the trapping of the particles involves the generation of resonant waves, a reassessment of the isotopic overabundance problem as well as a search for these waves in interplanetary space are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152983
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  • 6
    Electronic Resource
    Electronic Resource
    Cme Phenomenology in Different Solar Magnetic Scenarios (1997)
    Springer
    Astrophysics and space science 256 (1997), S. 373-376 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The existence of three magnetic scenarios with magnetic field intensities one order apart was considered. CMEs were associated to different solar activity phenomena and solar features showing different characteristics. Those associated to intense magnetic fields were more complex, having either more components or multiple emissions and a greater magnetic energy to particle acceleration conversion rate. On the other hand, simple CMEs were found to associate to weak magnetic fields. No evidence was found that the process that leads to CME starts before their detection at 1.6 solar radii. This indicates that the whole volume moves upward simultaneously, no matter how deep it reaches into the solar atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001172917872
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  • 7
    Electronic Resource
    Electronic Resource
    The structure of the interplanetary medium during the first stip interval (September–October 1975) and prerelease of energetic solar particles (1982)
    Springer
    Astrophysics and space science 84 (1982), S. 485-493 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An analysis of the interplanetary medium structure is made during STIP 1. (September–October, 1975). Using a simple extrapolation method a reconstruction of the stream lines is made which shows that the interplanetary space during this time period was very quiet. Such a behaviour is expected because this interval is close to the minimum of the solar cycle activity. The evolution of two fast solar wind streams, which dominated the interplanetary medium for very long time periods, is studied. A peculiar solar proton event, with onset time before the optical flare, is explained according to Elliot mechanism — i.e., that energetic particles are stored for a long time and released, sometimes, before the optical flare. These particles can be seen only when the interplanetary medium is very quiet, (without shock waves) and the flare very isolated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651327
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  • 8
    Electronic Resource
    Electronic Resource
    Energy Spectra of Accelerated Solar Protons From Different Sources – I. Reconstruction and Properties of the Source Spectrum (1999)
    Springer
    Solar physics 186 (1999), S. 381-400 
    Details
    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
    URL: http://dx.doi.org/10.1023/A:1005190525187
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  • 9
    Electronic Resource
    Electronic Resource
    The cosmic-ray 1.68-year variation: A clue to understand the nature of the solar cycle? (1996)
    Springer
    Solar physics 167 (1996), S. 409-417 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the maximum entropy method (MEM), the cosmic-ray power spectral density in the frequency range 3 × 10−9–2 × 10−7 Hz has been estimated for the period 1947–1990. Cosmic-ray intensity data were integrated from the ion chamber at Huancayo and the neutron monitor at Deep River, following the method of Nagashima and Morishita (1980). The estimated spectrum shows power-law dependence (f −1.62), with several peaks superimposed. Periodicities of the different peaks are identified and related to solar activity phenomena; most of them were reported in the past. Once the 11-yr variation is eliminated, the most prominent feature in the spectrum is a variation, not reported before, with a period of 1.68 yr (604.8 d). This peak is correlated with fluctuations of similar periodicities found in the southern coronal hole area and in large active regions. The importance that this variation may have to elucidate the solar magnetic flux emergence and the activity cycle is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146349
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  • 10
    Electronic Resource
    Electronic Resource
    The intense solar activity of march 1989 as a precursor for the occurrence of an ENSO by the end of 1989 (1990)
    Springer
    Solar physics 126 (1990), S. 195-199 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We studied the occurrence of ENSO (El Niño-Southern Oscillation) events in relation to solar activity conditions and we found that the events are distributed in two populations, one that could be associated with low latitude coronal holes which occur along the ascending phase of the cycle and the other one which could be related to polar holes present at the end of the descending phase. As highly anomalous solar activity, in terms of flares and coronal holes, occurred in March of this year, we propose that an ENSO event is likely to occur by the end of the year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00158307
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