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  • 11
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    Statistical evaluation of gamma-ray line observations (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The statistical reliability of reported positive observations of solar and cosmic gamma-ray lines has been evaluated. The relative probability that each measurement is due to a real source rather than to an accidental fluctuation in the background has been determined, and it is found that the results are statistically compelling in only a small fraction of the reported observations. At present, extreme caution must be exercised in drawing astrophysical conclusions from reports of the detection of cosmic gamma-ray lines.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
    Format: text
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  • 12
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    Gamma-ray observational constraints on the origin of the optical continuum emission from the white-light flare of 1980 July 1 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results are presented for the flare of July 1, 1980, which started at approximately 1627 UT and in which simultaneous measurements were made of X-ray, gamma-ray, and optical continuum emission for the entire duration of the flare. The X-ray and gamma-ray observations were made by the Gamma-Ray Spectrometer on the Solar Maximum Mission satellite. The optical measurements were taken at the Sacramento Peak Observatory and the Big Bear Solar Observatory (Zirin and Neidig, 1981). It is found that the major white-light emission that occurs in the late phase of the flare could not have been due to heating by electron or ion precipitation. This conclusion derives from the fact that the X-ray and gamma-ray flux peaks approximately 1 minute before the maximum of the optical continuum mission emission. It is also found that approximately 73 percent of the optical continuum emission, representing a spatially and temporally distinct bright point, follows this maximum with little or no X-ray or gamma-ray emission in the same period.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 272; Sept. 15
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  • 13
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    The starting conditions for an optically small solar gamma ray flare (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It is suggested that optically small gamma-ray flares result from gradual pre-flare acceleration of protons over approximately 1,000 s by a series of magnetohydrodynamic shocks in the low corona. A fraction of the accelerated protons are trapped in the corona where they form a seed population for future acceleration. If the shock acceleration is sufficiently rapid proton energies may exceed the gamma-ray production threshold and trigger gamma-ray emission. This occurs without the total flare energy being necessarily large. Magnetic field geometry is an important parameter.
    Keywords: SOLAR PHYSICS
    Type: SH-1.3-2 , 19th Intern. Cosmic Ray Conf - Vol. 4; p 82-85; NASA-CP-2376-VOL-4
    Format: application/pdf
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  • 14
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    The propagation of solar flare particles in a turbulent coronal loop (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Energetic solar flare particles, both electrons and protons, must survive the turbulent environment of a flaring loop and propogate to the lower corona or chromosphere in order to produce hard X-ray and gamma ray bursts. This plasma turbulence, often observed in soft X-ray line widths to be in excess of 100 km/s, is presumably capable of efficiently scattering the fast flare particles. This prevents to some degree the free streaming of accelerated particles and depending on the amplitude of the turbulence, restricts the particles to diffusive propagation along the length of the loop to the target chromosphere. In addition this turbulence is capable of performing additional acceleration of the fast particles by the second order Fermi mechanism. For compact flares with rise times 10s, the acceleration effect is small and the propagation of the particles is governed by spatial diffusion and energy loss in the ambient medium. The solution of the time dependent diffusion equation with velocity dependent diffusion and energy loss coefficients yields for the case of nonrelativistic protons particle precipitation rates which are necessary for calculating thick target gamma ray emission and also yields the total thin target emissivity.
    Keywords: SOLAR PHYSICS
    Type: SH-1.1-3 , 19th Intern. Cosmic Ray Conf - Vol. 4; p 1; NASA-CP-2376-VOL-4
    Format: application/pdf
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  • 15
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    The behaviour of minor species in the solar wind (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The flow of minor species in the solar wind is considered on the basis of a model in which all species are heated in an arbitrary manner as they leave the sun and the minor species interact with the background proton-electron plasma through the radial electric field associated with the latter and by means of Coulomb collisions. In order to produce satisfactory results in which the ions all move at more or less the same speed at the orbit of the earth, it is necessary to introduce heating functions such that each species is given energy in proportion to its mass. Coulomb collisions are found to be important as a means of removing energy from the heavier species close to the sun and bringing all species closer to thermal equilibrium at great distances from the sun. Substantial velocity differences can occur between species, especially close to the sun. Furthermore it is not difficult to construct solutions in which the bulk velocity of the helium ions exceeds that of the solar wind, as is often observed.
    Keywords: SOLAR PHYSICS
    Type: Zeitschrift fuer Geophysik; 41; 3, 19; 1975
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  • 16
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    COMPTEL upper limits on gamma-ray line emission from Supernova 1991T (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The imaging Compton telescope COMPTEL on board the Compton Gamma-Ray Observatory (CGRO) measures gamma-rays in the energy range 0.75-30 MeV with an energy resolution of 9.7% full width at half maximum (FWHM) at 1 MeV. From June 15 to 28, 1991 and again from October 3 to 17, 1991 the region containing the supernova SN 1991T was observed. A search for gamma-ray line emission from the supernova yields no detection of line emission from the supernova. 2 sigma upper limits for the two predicted lines at 847 keV and at 1.238 MeV of approximately equal to 3 x 10(exp -5) photons/(sq cm)(s) were derived. These limits are compared with the predictions of some theoretical models and constraints imposed by these limits on these models are discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 292; 2; p. 569-579
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  • 17
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    Comptel measurements of the gamma-ray burst GRB 930131 (1994)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: On 1993 January 31 at 1857:12 Universal Time (UT), the Imaging Compton Telescope COMPTEL onboard the Compton Gamma Ray Observatory (CGRO) detected the cosmic gamma-ray burst GRB 930131. COMPTEL's MeV imaging capability was employed to locate the source to better than 2 deg (1 sigma error radius) within 7 hr of the event, initiating a world-wide search for an optical and radio counterpart. The maximum likelihood position of the burst from the COMPTEL data is alpha(sub 2000) = 12h 18m, delta(sub 2000) = -9 deg 42 min, consistent with independent CGRO-Burst and Transient Source Experiment (CGRO-BATSE) and Energetic Gamma Ray Experiment Telescope (EGRET) locations as well as with the triangulation annulus constructed using BATSE and Ulysses timing data. The combined COMPTEL and EGRET burst data yield a better estimate of the burst location: alpha(sub 2000) = 12h 18m and delta(sub 2000) = -10 deg 21 min, with a 1 sigma error radius of 32 min. In COMPTEL's energy range, this burst was short, consisting of two separate spikes occurring within a approximately 1 s interval with a low intensity tail for approximately 1 s after the second spike. No statistically significant flux is present for a 30 s period after the main part of the burst. This is consistent with the EGRET data. The COMPTEL telescope events indicate a hard, power-law emission extending to beyond 10 MeV with a spectral index of -1.8 +/- 0.4. The rapid fluctuations and high intensities of the gamma-ray flux greater than 10 MeV place the burst object no farther than 250 pc if the burst emission is not beamed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 422; 2; p. L67-L70
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  • 18
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    Multiple relaxation and inhomogeneous broadening in resonance enhanced Raman scattering - Application to tunable infrared generation (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for differing sets of relaxation rates with emphasis on alkali metal vapors which have spontaneous emission dominated relaxation. The model is further expanded to include Doppler broadening and used to predict the peak gain as a function of detuning for a frequency doubled alexandrite laser-pumped cesium vapor gain cell.
    Keywords: LASERS AND MASERS
    Type: Applied Physics B - Photophysics and Laser Chemistry (ISSN 0721-7269); 48; 173-182
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  • 19
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    Time-dependent coronal shock acceleration of energetic solar flare particles (1986)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A global time-dependent model is presented for the coronal and interplanetary shock acceleration and propagation of energetic solar flare particles. The calculations are carried out to help prove that coronal shock acceleration of solar flare particles is responsible for energetic solar flare event data gathered in interplanetary space. The model is based on the theory of diffusive shock acceleration, and requires particle speeds to be much greater than bulk velocities. Also, sufficient scattering must occur upstream and downstream of the shock for the particle scattering mean free path to be smaller than the characteristic scale lengths, which causes the same particles to encounter the shock repeatedly. A spherically symmetric shock wave is assumed, which leads to the same emission configuration for impulsively and monoenergetically emitted particles. Consideration is given to acceleration by compression at the shock front, adiabatic deceleration in the divergent downstream flow, the temporal evolution of the shock and the three-dimensional geometry of the corona. The model is used to generate normalized proton omnidirectional distributions at 1 AU and at the shock front. The spectral exhibit trends similar to those in observational data, especially proton acceleration times and the proton distribution profiles at 1 AU.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 303; 829-842
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  • 20
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    Instabilities in a three-level coherently pumped laser (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A theory for a coherently pumped, homogeneously broadened laser is developed which predicts instability at excitations 1.6 times threshold. The system exhibits a period-doubling sequence, chaos, and a period-three window.
    Keywords: LASERS AND MASERS
    Type: Optics Communications (ISSN 0030-4018); 64; 54-58
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