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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 34 (1974), S. 181-184 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Assumptions inherent in the determination of coronal temperature from the decay rate of type III radio bursts are examined. It is suggested that no reliable temperature estimates can yet be made.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 35 (1974), S. 153-169 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effects of scattering and refraction on radio waves in the solar corona are considered for several different coronal models. By considering a source near the plasma level in a spherically symmetric corona and in a streamer enhancement superimposed on a spherically symmetric corona we obtain results relating to bursts of types I, II and III. From the results of these calculations it is suggested that estimates of coronal density derived from observations of type II and type III bursts are too high by a factor of 1.5 to 2; that there is considerabe doubt about the accuracy of coronal temperatures estimated from rate of decay of type III bursts; and that the duration of, and velocity dispersion in, the exciters of type III bursts have probably been over-estimated. The effects of scattering and refraction are also considered as they relate to observations and interpretations of harmonic source radiation patterns, drift pair bursts and spike bursts.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 36 (1974), S. 375-381 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The slowly varying component of solar centimeter wavelength radiation can often be attributed to thermal emission from density enhancements above an active region. This assertion is justified by the success in reproducing the observations by ray tracing calculations in appropriate coronal models. Similar components have been observed at meter wavelengths and thermal radiation from density enhancements has again been suggested as the emission mechanism. However ray tracing calculations at meter wavelengths, unlike those at centimeter wavelengths, must include both refraction and scattering effects for realistic modelling. In this study, in which scattering is included for the first time, it is shown that scattering may lead to lower emission from density enhancements rather than higher emission as predicted by models in which refraction alone is considered. This strongly suggests that the emission observed at meter wavelengths is of non-thermal origin.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 65 (1980), S. 397-404 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The planetary radio astronomy experiment on the Voyager spacecraft observed several type II solar radiobursts at frequencies below 1.3 MHz; these correspond to shock waves at distances between 20R ⊙ and 1 AU from the Sun. We study the characteristics of these bursts and discuss the information that they give on shock waves in the interplanetary medium and on the origin of the high energy electrons which give rise to the radioemission. The relatively frequent occurence of type II bursts at large distances from the Sun favors the hypothesis of the emission by a longitudinal shockwave. The observed spectral characteristics reveal that the source of emission is restricted to only a small portion of the shock. From the relation between type II bursts, type III bursts and optical flares, we suggest that some of the type II bursts could be excited by type III burst fast electrons which catch up the shock and are then trapped.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 7 (1969), S. 434-447 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Radio emission from the sun at a wavelength of 9.1 cm has been studied during the quiet sun years, 1964–65, using the Stanford spectroheliograph. A map of the quiet sun has been prepared and compared with a map produced using the same instrument in 1960. On the basis of ray tracing results the differences in the two maps can be explained by a decrease in the electron density by a factor of 1.4 at the equator and 1.1 at the poles. The slowly varying component of emission can be attributed to electron density enhancements by a factor of 2 to 5 over regions with dimension 2′ to 6′ arc. Changes of flux and width of these regions with longitude on the sun agree with the results of ray tracing using a very simple model for the regions. The detection of sunspot groups on the far side of the sun by measuring increased 9.1 cm emission at the limbs is shown to be possible.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 44 (1975), S. 417-427 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cinematographic observations of solar prominences made at Mauna Loa during the past couple of years suggest that there is a well-defined sub-class of ascending prominences characterized by closed-system transference of chromospheric material along an arch or loop (up one leg and down the other); meanwhile the entire prominence envelope steadily rises upward and expands through the corona. We denote these prominences as ‘fountains’. Several examples are described. Fountains appear to be well contained by coronal magnetic fields. Their total kinetic energy is in the order of 1030 erg but dissipation is typically quite slow (over time periods like 100 min) so that the correlative disturbances (radio bursts, coronal transients, chromopsheric brightenings, etc.) are generally unspectacular or non-existent.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 6 (1969), S. 251-254 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The slowly varying component of solar microwave emission is associated with plage and sunspot regions seen optically. Under the assumption that the microwave emission originates radially above the associated optical feature the height of the microwave emission region above the photosphere can be calculated. For 99 regions seen at 9.1 cm during the International Quiet Sun Years 1964–1965 the average height was 8000 km. This result compares with 18000 km measured for the same wavelength emission during 1960. A change of height in this direction could be the result of the changing strength of the magnetic field associated with regions seen during the two periods.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 13 (1970), S. 448-457 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The 80 MHz emission from a moving type IV source has been observed as the source moved from 2 to 51/4 R ⊙ from the centre of the Sun. The emission came from a plasma cloud ejected in association with an extensive solar prominence. The cloud appeared to move with a speed (∼ 270 km/sec) approximating the local Alfvén velocity in the corona. At 2 R ⊙ the emission was from a single unpolarized source, while at 5 R ⊙ it was from two sources strongly circularly polarized in opposite senses. The physical conditions inside and outside the source and the emission mechanisms are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 21 (1977), S. 309-327 
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The planetary radio astronomy experiment will measure radio spectra of planetary emissions in the range 1.2 kHz to 40.5 MHz. These emissions result from wave-particle-plasma interactions in the magnetospheres and ionospheres of the planets. At Jupiter, they are strongly modulated by the Galilean satellite Io. As the spacecraft leave the Earth's vicinity, we will observe terrestrial kilometric radiation, and for the first time, determine its polarization (RH and LH power separately). At the giant planets, the source of radio emission at low frequencies is not understood, but will be defined through comparison of the radio emission data with other particles and fields experiments aboard Voyager, as well as with optical data. Since, for Jupiter, as for the Earth, the radio data quite probably relate to particle precipitation, and to magnetic field strength and orientation in the polar ionosphere, we hope to be able to elucidate some characteristics of Jupiter auroras. Together with the plasma wave experiment, and possibly several optical experiments, our data can demonstrate the existence of lightning on the giant planets and on the satellite Titan, should it exist. Finally, the Voyager missions occur near maximum of the sunspot cycle. Solar outburst types can be identified through the radio measurements; when the spacecraft are on the opposite side of the Sun from the Earth we can identify solar flare-related events otherwise invisible on the Earth.
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  • 10
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