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  • SOLAR PHYSICS  (45)
  • 1980-1984
  • 1975-1979  (45)
  • 1935-1939
  • 1979  (45)
  • 11
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    Principal component analysis of solar flares in the soft X-ray flux (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The paper considers principal component analysis of solar flares in the soft X-ray flux, a technique for extracting the salient features from a mass of data. The method applies particularly to the analysis of nonstationary ensembles, and its computations require the evaluation of eigenvalues of matrices. The Eispack matrix eigen system routines were used to analyze full-disk proportional-counter data from the X-ray event analyzer which was part of the Skylab experiment. Empirical orthogonal functions were derived for events in the soft X-ray spectrum between 2.5 and 20 A during different time periods, indicating that about 90% of the cumulative power of each analyzed flare is contained in the largest eigenvector. The first two largest eigenvectors are sufficient for an empirical curve fit through the raw data and a characterization of solar flares in the soft X-ray flux, and power spectra of two largest eigenvectors reveal a reported periodicity of about 5 min.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 80; 2, De; Dec. 197
    Format: text
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  • 12
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    The core electron temperature profile between 0.5 and 1.0 AU in the steady-state high speed solar wind (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 84; Aug. 1
    Format: text
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  • 13
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    A theory of local and global processes which affect solar wind electrons. I - The origin of typical 1 AU velocity distribution functions - Steady state theory (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A kinetic theory for the velocity distribution of solar wind electrons which illustrates the global and local properties of the solar wind expansion is proposed. By means of the Boltzmann equation with the Krook collision operator accounting for Coulomb collisions, it is found that Coulomb collisions determine the population and shape of the electron distribution function in both the thermal and suprathermal energy regimes. For suprathermal electrons, the cumulative effects of Coulomb interactions are shown to take place on the scale of the heliosphere itself, whereas the Coulomb interactions of thermal electrons occur on a local scale near the point of observation (1 AU). The bifurcation of the electron distribution between thermal and suprathermal electrons is localized to the deep solar corona (1 to 10 solar radii).
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 84; June 1
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  • 14
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    The high-temperature corona associated with a loop prominence system (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Flare-associated coronal loops were observed on the SE limb of the sun of 1972 February 9 by the Goddard X-ray and EUV spectroheliograph on board OSO 7. The loop structure is clearly visible in the lines of Mg VIII and Mg IX, whereas little or no detail is observed in Fe XV and Fe XVI. A looplike structure with a cloud of emission at the top is observed in soft X-rays. The temperature structure in the region has been calculated from the ratio Fe XVI/Fe XV. The isothermal contour plot is strikingly similar to the isointensity contour plots of the soft X-ray spectroheliograms. With these temperatures and the Fe XV intensity calculated from a calibration scheme developed by Chapman and Neupert, the emission measure has been estimated in the loops. Calculated energy losses suggest that continued deposition of energy is required over the observing period.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 15
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    The gyrosynchrotron emission from quasi-thermal electrons and applications to solar flares (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 16
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    High-resolution observations of the quiet sun at 6 centimeters using the Westerbork Synthesis Radio Telescope (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 17
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    Observation of an impulsive solar X-ray burst from a coronal source (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Observations of the spatial, spectral, and temporal structure of an impulsive hard X-ray source in a behind-the-limb solar flare have been made with high-time-resolution hard X-ray detectors aboard two spacecraft, the International Sun Earth Explorer 3 (ISEE 3) and the Pioneer Venus Orbiter (PVO), which were separated in heliographic longitude by about 12.5 deg. The principal findings are that (1) the coronal part of the X-ray source is about 600 times less intense than the lower-altitude part of the source; and (2) the coronal X-ray observations are consistent with a power-law electron spectrum which extends down to about 5 keV.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 18
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    The energy balance and pressure in the solar transition zone for network and active region features (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The electron pressure and energy balance in the solar transition zone are determined for about 125 network and active region features on the basis of high spectral and spatial resolution extreme ultraviolet spectra. Si III line intensity ratios obtained from the Naval Research Laboratory high-resolution telescope and spectrograph during a rocket flight are used as diagnostics of electron density and pressure for solar features near 3.5 x 10 to the 4th K. Observed ratios are compared with the calculated dependence of the 1301 A/1312 A and 1301 A/1296 A line intensity ratios on electron density, temperature and pressure. Electron densities ranging from 2 x 10 to the 10th/cu cm to 10 to the 12th/cu cm and active region pressures from 3 x 10 to the 15th to 10 to the 16th/cu cm K are obtained. Energy balance calculations reveal the balance of the divergence of the conductive flux and turbulent energy dissipation by radiative energy losses in a plane-parallel homogeneous transition zone (fill factor of 1), and an energy source requirement for a cylindrical zone geometry (fill factor less than 0.04).
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 233
    Format: text
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  • 19
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    Ion sound turbulence in the solar wind (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A stability analysis for ion sound is carried out in order to contribute to clarifying the mechanism of some observed fluctuations, which directly uses detailed measured particle distributions rather than model distributions. Correlation with measured wave activity is satisfactory. Valuable information about the instability mechanism, transport processes, and the accuracy of measured distributions can be obtained by this method. An illustration from Helios 1 data is presented.
    Keywords: SOLAR PHYSICS
    Type: Contrib. to the 4th Solar Wind Conf.; p 1-6
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  • 20
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    An empirical polytrope law for solar wind thermal electrons between 0.45 and 4.76 AU: Voyager 2 and Mariner 10 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Empirical evidence is presented that solar wind thermal electrons obey a polytrope law with polytrope index gamma = 1.175 plus or minus 0.03. The Voyager 2 and Mariner 10 data used as evidence are compared and discussed. The theoretical predictions that solar wind thermal electrons in the asymptotic solar wind should obey a polytrope law with polytrope index gamma = 1.16 plus or minus. The widespread impressions in the literature that solar wind electrons behave more like an isothermal than adiabatic gas, and the arguments that Coulomb collisions are the dominant stochastic process shaping observed electron distribution functions in the solar wind are reexamined, reviewed and evaluated. The assignment of the interplanetary potential as equal to approximately seven times the temperature of the thermal electrons is discussed.
    Keywords: SOLAR PHYSICS
    Type: NASA-TM-80594
    Format: application/pdf
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