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  • 1
    Electronic Resource
    Electronic Resource
    Energetics of a double flare on November 8, 1980 (1985)
    Springer
    Solar physics 98 (1985), S. 141-158 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Here we complete an energy balance analysis of a double impulsive hard X-ray flare. From spatial observations, we deduce both flares probably occur in the same loop within the resolution of the data. For the first flare, the energy in the fast electrons (assuming a thick-target model) is comparable to the convective up-flow energy, suggesting that these are related successive modes of energy storage and transfer. The total energy lost through radiation and conduction, 2.0 × 1028 erg, is comparable to the energy in fast electrons 2.5 × 1028 erg. For the second flare, the energy in the fast electrons is more than one order of magnitude greater than the energy of the convective up-flow. Total energy losses are within a factor of two lower than the calculated fast electron energy. We interpret the observations as showing that the first flare occurred in a small loop with fast electrons heating the chromosphere and resulting in chromospheric evaporation increasing the density in the loop. For the second flare most of the heating occurred at the electron acceleration site. The two symmetrical components of the Ca xix resonance line and a high velocity down-flow of 115 km s −1 observed at the end of the second hard X-ray burst are consistent with the flare eruption (reconnection) region being high in the flare loop. The estimated altitude of the acceleration site is 5500 km above the photosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00177204
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  • 2
    Electronic Resource
    Electronic Resource
    Solar burst with millimetre-wave emission at high frequency only (1985)
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 380-382 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Past observations at centimetre-millimetre wavelengths indicate that certain bursts can display turnover frequencies which are higher than 30 GHz (l 〈 10 mm)4-9. One very large burst exhibited a spectral 'flattening' in the range 30-71 GHz (refs 4, 5), which was also found for a few other ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/313380a0
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  • 3
    Electronic Resource
    Electronic Resource
    The 78.4-day period of Cygnus XR-1 (1979)
    [s.l.] : Nature Publishing Group
    Nature 280 (1979), S. 126-127 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Analysis of the power spectrum of the U-band polarisation of HDE226868 on 225 nights between 1974 and 1977 led to the original detection by Kemp et al.2 of a 39.2-d modulation in the magnitude of polarisation with peak-to-peak amplitude of 0.25% (or 0.0054 mag). A modulation with a 78.4-d period ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/280126a0
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray observations of AM Herculis from OSO 8 (1979)
    [s.l.] : Nature Publishing Group
    Nature 279 (1979), S. 509-510 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The OSO 8 instruments used to observe AM Her consist of a proportional counter7 covering the photon energy range 2-40 keV, and a high energy scintillation spectrometer8 covering the range 20-250 keV. The source was observed during the period 1-10 October 1977. The results presented here from the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/279509a0
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  • 5
    Electronic Resource
    Electronic Resource
    High energy X-ray spectrum of Her X-1 (1978)
    [s.l.] : Nature Publishing Group
    Nature 275 (1978), S. 195-197 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The discovery by Triimper et al.5,6 of two strong lines in the pulsed X-ray spectrum of Her X-1 has inspired many other groups to search for this phenomenon. The stronger of the two lines, at 5 8 ± 5 keV, has now been observed by Trumper et al. on two separate balloon flights, one in May ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/275195a0
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  • 6
    Electronic Resource
    Electronic Resource
    Intensity transitions in Cyg XR-1 observed at high energies from OSO 8 (1977)
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 813-815 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Cyg XR-1 was observed with the high energy X-ray spectrometer on board the OSO-8 satellite from 11 to 19 November, 1975, and from 27 October to 15 November, 1976 (excluding the period from 1 November to 7 November, 1976). The CsI(Na) scintillation spectrometer is sensitive to radiation in the 20 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/267813a0
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  • 7
    Electronic Resource
    Electronic Resource
    The Hard X-Ray Burst Spectrometer on the Solar Maximum Mission (1980)
    Springer
    Solar physics 65 (1980), S. 25-37 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The primary scientific objectives of the Hard X-Ray Burst Spectrometer (HXRBS) to be flown on the Solar Maximum Mission are as follows: (1) To determine the nature of the mechanisms which accelerate electrons to 20–100 keV in the first stage of a solar flare and to 〉 1 MeV in the second stage of many flares; and (2) to characterize the spatial and temporal relation between electron acceleration, storage and energy loss throughout a solar flare. Measurements of the spectrum of solar X-rays will be made in the energy range from 20 to 260 keV using an actively-shielded CsI(Na) scintillator with a thickness of 0.635 cm and a sensitive area of 71 cm2. Continuous measurements with a time resolution of 0.128 s will be made of the 15-channel energy-loss spectrum of events in this scintillator in anticoincidence with events in the CsI(Na) shield. Counting-rate data with a time resolution as short as 1 ms will also be available from a limited period each orbit using a 32K-word circulating memory triggered by a high event rate. In the first year after launch, it is expected that approximately 1000 flares will be observed above the instrument sensitivity threshold, which corresponds to a 20–200 keV X-ray flux of 2 × 10−1 photons (cm2 s)−1 lasting for at least one second.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151382
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  • 8
    Electronic Resource
    Electronic Resource
    Microwave and hard X-Ray observations of a solar flare with a time resolution better than 100 ms (1983)
    Springer
    Solar physics 84 (1983), S. 311-319 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Simultaneous microwave and X-ray observations are presented for a solar flare detected on May 8, 1980 starting at 19:37 UT. The X-ray observations were made with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission and covered the energy range from 28–490 keV with a time resolution of 10 ms. The microwave observations were made with the 5 and 45 foot antennas at the Itapetinga Radio Observatory at frequencies of 7 and 22 GHz, with time resolutions of 100 ms and 1 ms, respectively. Detailed correlation analysis of the different time profiles of the event show that the major impulsive peaks in the X-ray flux preceded the corresponding microwave peaks at 22 GHz by about 240 ms. For this particular burst the 22 GHz peaks preceded the 7 GHz by about 1.5 s. Observed delays of the microwave peaks are too large for a simple electron beam model but they can be reconciled with the speeds of shock waves in a thermal model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157464
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  • 9
    Electronic Resource
    Electronic Resource
    Observation of chromospheric evaporation during the solar maximum mission (1983)
    Springer
    Solar physics 86 (1983), S. 67-77 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A sample of flares detected in 1980 with the Bent Crystal Spectrometer and the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission satellite has been analysed to study the upward motions of part of the soft X-ray emitting plasma. These motions are inferred from the presence of secondary blue-shifted lines in the Ca XIX and Fe XXV spectral regions during the impulsive phase of disk flares. Limb flares do not show such blue-shifted lines indicating that the direction of the plasma motion is mainly radial and outward. The temporal association of these upward motions with the rise of the thermal phase and with the impulsive hard X-ray burst, as well as considerations of the plasma energetics, favour the interpretation of this phenomenon in terms of chromospheric evaporation. The two measureable parameters of the evaporating plasma, emission measure and velocity, depend on parameters related to the energy deposition and to the thermal phase. The evaporation velocity is found to be correlated with the spectral index of the hard X-ray flux and with the rise time of the thermal emission measure of the coronal plasma. The emission measure of the rising plasma is found to be correlated with the total energy deposited by the fast electrons in the chromosphere by collisions during the impulsive phase and with the maximum emission measure of the coronal plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157175
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  • 10
    Electronic Resource
    Electronic Resource
    Fast transients in hard X-ray solar flares (1983)
    Springer
    Solar physics 86 (1983), S. 239-240 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results of a search for fast spikes in 5483 hard X-ray solar flares as observed with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission (SMM). Hundreds of fast spikes with durations of less than 1 second have been detected at time resolutions of 128 ms and 10 ms. Fast spikes have been detected with rise and decay times as short as 20 ms and with widths as short at 45 ms that represent the fastest hard X-ray variations yet seen from the Sun. The observations of such fast variations place new constraints on the physical nature of the source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157195
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