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  • 1
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    COMPTEL solar flare observations (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: COMPTEL as part of a solar target of opportunity campaign observed the sun during the period of high solar activity from 7-15 Jun. 1991. Major flares were observed on 9 and 11 Jun. Although both flares were large GOES events (greater than or = X10), they were not extraordinary in terms of gamma-ray emission. Only the decay phase of the 15 Jun. flare was observed by COMPTEL. We report the preliminary analysis of data from these flares, including the first spectroscopic measurement of solar flare neutrons. The deuterium formation line at 2.223 MeV was present in both events and for at least the 9 Jun. event, was comparable to the flux in the nuclear line region of 4-8 MeV, consistent with Solar-Maximum Mission (SSM) Observations. A clear neutron signal was present in the flare of 9 Jun. with the spectrum extending up to 80 MeV and consistent in time with the emission of gamma-rays, confirming the utility of COMPTEL in measuring the solar neutron flux at low energies. The neutron flux below 100 MeV appears to be lower than that of the 3 Jun. 1982 flare by more than an order of magnitude. The neutron signal of the 11 Jun. event is under study. Severe dead time effects resulting from the intense thermal x-rays require significant corrections to the measured flux which increase the magnitude of the associated systematic uncertainties.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 470-479
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  • 2
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    High energy flare physics group summary (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The contributions of the High Energy Flare Physics Special Session in the American Astronomical Society Solar Physics Division Meeting are reviewed. Oral and poster papers were presented on observatories and instruments available for the upcoming solar maximum. Among these are the space-based Gamma Ray Observatory, the Solar Flare and Cosmic Burst Gamma Ray Experiment on the Ulysses spacecraft, the Soft X Ray Telescope on the spacecraft Solar-A, and the balloon-based Gamma Ray Imaging Device. Ground based observatories with new capabilities include the BIMA mm-wave interferometer (Univ. of California, Berkeley; Univ. of Illinois; Univ. of Maryland), Owens Valley Radio Observatory and the Very Large Array. The highlights of the various instrument performances are reported and potential data correlations and collaborations are suggested.
    Keywords: SOLAR PHYSICS
    Type: NASA, Goddard Space Flight Center, Max '91 Workshop 2: Developments in Observations and Theory for Solar Cycle 22; p 1-16
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  • 3
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    The propagation of solar flare particles in a coronal loop (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A time-dependent diffusion equation with velocity-dependent diffusion and energy-loss coefficients was solved for the case where energetic solar particles are injected into a coronal loop and then diffuse out the ends of the loop into the lower corona/chromosphere. The solution yields for the case of relativistic electrons, precipitation rates and populations which are necessary for calculating thick and thin target X-ray emission. It follows that the thick target emission is necessarily delayed with respect to the particle acceleration on injection by more than the mere travel time of the particle over the loop length. In addition the time-dependent electron population at the top of the loop is calculated. This is useful in estimating the resulting micron-wave emission. The results show relative timing differences in the different emission processes which are functions of particle species, energy and the point of injection of the particles into the loop. Equivalent quantities are calculated for non-relativistic protons.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Rapid Fluctuations in Solar Flares; p 383-392
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  • 4
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    Spatial variation for flares observed with the gamma ray spectrometer aboard the SMM satellite (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A search is made for anisotropic X-ray bremsstrahlung photon production from relativistic electrons by studying the heliocentric angular dependence of 53 flares detected at energies above 300 keV. No evidence is found for a higher rate of detectable flares near the limb at the 80 percent confidence level. This result implies that the X-ray directivity as defined by the ratio of photon intensity at 75 deg and 0 deg of heliocentric angle is less than 1.5 above 300 keV and strongly rejects any flare model predicting X-ray production from a radial 'beam' of energetic electrons.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 5
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    A direct observation of solar neutrons following the 0118 UT flare on 1980 June 21 (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Gamma Ray Spectrometer on the Solar Maximum Mission satellite has observed energetic solar neutrons (greater than 50 MeV) at the earth following a solar flare that occurred on the west limb on June 21, 1980 at 01:18:20 UT. Impulsive photon emission from 10 keV to greater than 65 MeV lasting over a period of about 66 s was followed by a transient flux of 50-600 MeV neutrons incident over a 17 minute period. The peak counting rate corresponds to an average flux at the earth of (3.8 + or - 0.6) x 10 to the -2nd neutrons/sq cm s at 130 MeV. These observations indicate the emission of 3 x 10 to the 28th neutrons/sr with energies greater than 50 MeV, requiring the rapid acceleration (much less than 60 s) of protons to GeV energies during the impulsive phase of the flare.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 263
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  • 6
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    Observations with the SMM gamma-ray spectrometer - The impulsive solar flares of 1980 March 29 (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Gamma-ray continuum emission from 0.3 to 1 MeV was observed with the gamma-ray spectrometer on the Solar Maximum Mission satellite during two impulsive solar flares on 1980 March 29, from active region 2363 at 0918 UT and from active region 2357 at 0955 UT. Evidence is presented for a hardening of the spectrum during the impulsive phase of the flares. The photon intensity greater than 100 keV appears to decay at a slower rate than that at lower energies. Time-integrated photon spectra for both flares are incompatible with a single-temperature thermal-bremsstrahlung model. Upper limits for prompt and delayed gamma-ray lines are presented.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 7
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    Observation of the 2.223 MeV gamma-ray line on the SMM satellite - The event of 1980 June 7 (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 8
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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
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    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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  • 9
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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
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  • 10
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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
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