E. L. Chupp

A direct observation of solar neutrons following the 0118 UT flare on 1980 June 21

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.

Spectral evolution of pulse structures in gamma-ray bursts

The Hard X-Ray Burst Spectrometer (HXRBS) and Gamma-Ray Spectrometer (GRS) data from the Solar Maximum Mission satellite have been searched for gamma-ray bursts with sufficient intensities and relatively simple time profiles such that their spectral behavior may be studied on a time scale of about 1 s. Ten such events were observed with the GRS experiment, and four of these were also detected within the HXRBS field of view. Details are presented for two moderately intense bursts with relatively simple structure. The spectral evolutions of the remaining events are summarized briefly. Results suggest a pattern in the spectral evolution within burst pulses: a tendency for the high-energy emission to lead the low-energy emission, in contrast to the correlation of intensity and spectral hardness reported by Golenetskii et al. (1983).

The gamma ray spectrometer for the Solar Maximum Mission

The Solar Maximum Mission Gamma Ray Experiment (SMM GRE) utilizes an actively shielded, multicrystal scintillation spectrometer to measure the flux of solar gamma rays. The instrument provides a 476-channel pulse height spectrum (with energy resolution of ∼7% at 662 keV) every 16.38 s over the energy range 0.3–9 MeV. Higher time resolution (2 s) is available in three windows between 3.5 and 6.5 MeV to study prompt gamma ray line emission at 4.4 and 6.1 MeV. Gamma ray spectral analysis can be extended to ≳15 MeV on command. Photons in the energy band from 300–350 keV are recorded with a time resolution of 64 ms. A high energy configuration also gives the spectrum of photons in the energy range from 10–100 MeV and the flux of neutrons ≳20 MeV. Both have a time resolution of 2 s. Auxiliary X-ray detectors will provide spectra with 1-sec time resolution over the energy range of 10–140 keV. The instrument is designed to measure the intensity, energy, and Doppler shift of narrow gamma ray lines as well as the intensity of extremely broadened lines and the photon continuum. The main objective is to use this time and spectral information from both nuclear gamma ray lines and the photon continuum in a direct study of the dynamics of the solar flare/particle acceleration phenomena.

Detection of galactic Al-26 gamma radiation by the SMM spectrometer

The gamma-ray spectrometer on the Solar Maximum Mission Satellite has detected a line near 1.81 MeV with a significance of >5 sigma in each of 3 yr when the Galactic center traversed the broad aperture of the instrument in 1980, 1981, and 1982. There was no significant variation in intensity from year to year. The Galactic center/anticenter intensity ratio is >2.5, and the center of the emission is consistent with the location of the Galactic center. The distribution could not be measured well enough to distinguish between candidate sources, e.g., novae, supernovae, red giants, and massive stars. For an assumed source distribution which follows the >100 MeV Galactic gamma radiation, the total flux measured in the direction of the Galactic center is (4.0 +- 0.4) x 10/sup -4/ ..gamma..(cm/sup 2/ s rad)/sup -1/. The measured energy of the line is 1.804 +- 0.004 MeV. These measurements are consistent with the detection of a narrow ..gamma..-ray line from interstellar /sup 26/Al by HEAO 3 in 1979/1980.

The Solar Maximum Mission Atlas of Gamma-Ray Flares

We present a compilation of data for all 258 gamma-ray —ares detected above 300 keV by the Gamma Ray Spectrometer (GRS) aboard the Solar Maximum Mission satellite. This gamma-ray —are sample was collected during the period from 1980 February to 1989 November; covering the latter half of the 21st solar sunspot cycle and the onset of the 22d solar sunspot cycle. We describe the SMM/GRS instrument, its in-orbit operation, and the principal data reduction methods used to derive the gamma-ray —are properties. Utilizing measurements for 185 —ares that were sufficiently intense to allow the derivation of gamma-ray spectra, we present an atlas of time pro—les and gamma-ray spectra. The —are parameters derived from the gamma-ray spectra include bremsstrahlung —uence and best-—t power-law parameters, narrow nuclear line —uence, positron annihilation line —uence, neutron capture line —uence, and an indi- cation of whether or not emissions greater than 10 MeV were present. Since a uniform methodology was adopted for deriving the parameters, this atlas should be very useful for future statistical and correlative studies of solar —ares. Subject headings: catalogsgamma rays: burstsSun: —ares

High-energy emission in gamma-ray bursts

Between February 1980 and August 1983 the Gamma-Ray Spectrometer on the Solar Maximum Mission Satellite (SMM) detected 72 events identified as being of cosmic origin. These events are an essentially unbiased subset of all gamma-ray bursts. The measured spectra of these events show that high energy (greater than 1 MeV) emission is a common and energetically important feature. There is no evidence for a general high-energy cut-off or a distribution of cut-offs below about 6 MeV. These observations imply a limit on the preferential beaming of high energy emission. This constraint, combined with the assumption of isotropic low energy emission, implies that the typical magnetic field strength at burst radiation sites is less than 1 x 10 to the 12th gauss.

Very energetic gamma-rays from the 3 June 1982 solar flare

Abstract The Gamma-Ray Spectrometer on the Solar Maximum Mission satellite has recorded high energy gamma-ray and neutron emission from the flare on 3 June 1982. During the 65 sec. impulsive phase the gamma rays > 10 MeV contains emissions from both primary electron bremsstrahlung and nuclear pion decay. Hence the impulsive phase acceleration process must produce both primary electrons with energies > 60 MeV and ions >500 MeV. This flare also has a extended emission phase lasting more than 1000 sec which is most easily observed at gamma-ray energies > 10 MeV. After removing the counting rates from the more slowly moving neutrons produced at earlier times, the resulting gamma ray spectrum can be entirely explained by nuclear pion production. We find that >70 % of the pions were produced in the extended emission phase. In contrast, more than 70 % of the high energy primary electron bremsstrahlung and the

High energy neutron and pion-decay gamma-ray emissions from solar flares

Solar flare gamma-ray emissions from energetic ions and electrons have been detected and measured to GeV energies since 1980. In addition, neutrons produced in solar flares with 100 MeV to GeV energies have been observed at the Earth. These emissions are produced by the highest energy ions and electrons accelerated at the Sun and they provide our only direct (albeit secondary) knowledge about the properties of the accelerator(s) acting in a solar flare. The solar flares, which have direct evidence for pion-decay gamma-rays, are unique and are the focus of this paper. We review our current knowledge of the highest energy solar emissions, and how the characteristics of the acceleration process are deduced from the observations. Results from the RHESSI, INTEGRAL and CORONAS missions will also be covered. The review will also cover the solar flare capabilities of the new mission, FERMI GAMMA RAY SPACE TELESCOPE, launched on 2008 June 11. Finally, we discuss the requirements for future missions to advance this vital area of solar flare physics.

Emission characteristics of three intense solar flares observed in cycle 21

The available observational data is reviewed, for three solar flares, that occurred on June 21, 1980, June 3, 1982, and April 24, 1984. Inperpretations given prior to the time of this workshop and some interpretations presented at the workshop are considered. A possible common model describing the three flares is also discussed. It is clear that more refined analysis of all available data for these three events is very desirable and could lead to improved understanding of the flare process. 77 refs.

A balloon-borne coded aperture telescope for low-energy gamma-ray astronomy

Abstract A telescope for imaging cosmic γ-ray emission over the energy range 160 keV to 9.3 MeV has been developed and successfully flown on a high altitude balloon over Palestine, Texas on 1 October, 1984. This instrument consists of a coded mask based on a 5 × 7 uniformly redundant array (URA) and a scintillator array consisting of 35 bismuth germanate (BGO) detectors. The telescope can image sources with an intrinsic resolution of 3.8° within a 15.2° × 22.8° field of view. The properties of the instrument are described and its imaging capability is demonstrated with results from an observation of the region of the Crab Nebula. The imaging response to the Crab was found to be well represented by a bivariate Gaussian function of full width at half-maximum (FWHM) 4.8°. The centroid of the response was determined to a precision of ± 12 arc min.