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Forrest, D. J.

Publications and source records attributed to Forrest, D. J..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Gamma ray spectroscopy in astrophysics: Solar gamma ray astronomy on solar maximum mission

The SMM gamma ray experiment and the important scientific capabilities of the instrument are discussed. The flare size detectable as a function of spectrum integration time was studied. A preliminary estimate indicates that a solar gamma ray line at 4.4 MeV one-fifth the intensity of that believed to have been emitted on 4 August 1972 can be detected in approximately 1000 sec with a confidence level of 99%.

Forrest, D. J.↗
NASA NTRS1975

Solar gamma rays and other nuclear secondaries

Observations of solar gamma rays and nuclear secondaries associated with flares provide a direct probe into the behavior of energetic solar particles and the conditions under which they are accelerated, stored, and released on the sun. During the August 1972 series of solar events, gamma ray lines at 0.51, 2.23, 4.4, and 6.1 MeV and isotopes of H and He were detected. These experimental results and the present status of their interpretation are reviewed. The constraints that these observations have on general solar flare particle acceleration models are also discussed.

Forrest, D. J.↗
NASA NTRS1975

High energy gamma-ray radiation above 300 keV associated with solar activity

The present state of knowledge about the production of gamma-ray lines and continuum during the impulsive phase of solar flares is reviewed. It is noted that the only definite evidence for gamma rays associated with solar flares was obtained by OSO 7 during the events of August 4 and 7, 1972. This experimental evidence is examined, and gamma-ray line emission mechanisms are discussed, particularly positron annihilation through positronium formation. It is shown that if all the data are taken into account, neither the preflare nor the postflare accumulation model for gamma-ray emission can be ruled out.

Chupp, E. L.↗
NASA NTRS1975

Observation of radioactive background in the OSO-7 gamma ray monitor

The counting rate as measured by the gamma ray monitor on the OSO-7 satellite, covering the energy range 0.3-10 MeV, during a sixteen month period (October 1971-December 1972) was considerably higher than expected from balloon data previously reported. Dyer et al. (1971) have shown the importance of activation in satellites for diffuse gamma flux measurements. The OSO-7 spectra exhibit strong, complex line structure, especially between 400 keV and 900 keV, and several identifications can be made consistent with the model of Dyer et al. The spectral structure and time variations are presented which must be explained by any activation model.

Dunphy, P. P.↗
NASA NTRS1974

Solar gamma ray monitor for OSO-H (0.3-10 MeV)

A gamma ray experiment to be flown aboard the OSO-7 spacecraft is described along with a history of the development of the experiment, a description of the gamma ray detector and its operation, and a short preliminary review of the scientific information obtained during the instruments' lifetime. The gamma ray detector operated an average of 18 hours a day for approximately 15 months. The majority of the data was collected in the solar and antisolar direction, but data at right angles to the spacecraft-sun line was also accumulated. In all, at least two full scans of the celestial sphere were completed.

Chupp, E. L.↗
NASA NTRS1974

Search for gamma ray lines from supernovae and supernova remnants

A gamma ray monitor with a NaI crystal shielded with a cup-shaped CsI cover was contained in the rotating wheel compartment of the OSO-7 spacecraft for measuring the gamma ray spectra from 0.3 to 10 MeV in search for gamma ray lines from a possible remnant in the Gum Nebula and the apparent Type I supernovae in NGC5253. A brief analysis of data yielded no positive indications for X-rays, gamma ray lines, or continuum from these sources.

Chupp, E. L.↗
NASA NTRS1974

Gamma ray observations during the August 1972 solar activity

During the solar activity period in August 1972, the UNH gamma ray monitor on the OSO-7 satellite measured gamma ray line and continuum fluxes of solar origin on at least two occasions; August 4 and 7. In this discussion, the experiment and the gamma ray line observations are reviewed with a few brief remarks on interpretation. The specific observations discussed are measurements of gamma ray lines at 0.51 and 2.2 MeV during two of the largest optical solar flares. Evidence for lines at other energies is also given.

Chupp, E. L.↗
NASA NTRS1973

Documentation of the data analysis system for the gamma ray monitor aboard OSO-H

The programming system is presented which was developed to prepare the data from the gamma ray monitor on OSO-7 for scientific analysis. The detector, data, and objectives are described in detail. Programs presented include; FEEDER, PASS-1, CAL1, CAL2, PASS-3, Van Allen Belt Predict Program, Computation Center Plot Routine, and Response Function Programs.

Croteau, S.↗
NASA NTRS1973

Observations of Gamma-ray Emission in Solar Flares

The observations of gamma ray emission made from the OSO-7 satellite in connection with two solar flares in early August 1972 are reported. The details of the measurements and a preliminary interpretation of some of the observed features are given.

Forrest, D. J.↗
NASA NTRS1973

Gamma ray and neutron measurements and their relation to the solar flare problem.

In order to interpret recent observations of solar gamma ray lines from OSO-7, we consider the possible nuclear reactions which can occur and assess their relative importance in the solar environment. This analysis shows that about 3 times 10 to the 32nd power protons (energy greater than 30 MeV) must have been produced during the initial phase of the flare on Aug. 4, 1972. The ability to determine the temperature in the solar region where the positrons annihilate has been estimated from the 0.51 MeV line width, giving a temperature there of less than 7 million deg K. The major conclusions from these observations are discussed and some outstanding problems are mentioned. Finally, requirements for the next generation of solar gamma ray and neutron experiments are discussed.

Chupp, E. L.↗
NASA NTRS1973

Observations of gamma-ray emission in solar flares

Solar flare associated gamma ray observations are reviewed. Data cover He-3, line emission, and absolute intensity associated with gamma ray production. Results are given in graphs and tables.

Forrest, D. J.↗
NASA NTRS1973

Solar gamma ray and neutron observations

The present status of knowledge concerning the impulsive and the continuous emission of solar gamma rays and neutrons is reviewed in the light of the recent solar activity in early August 1972. The gamma ray spectrometer on Orbiting Solar Observatory-7 (OSO-7) has observed the sun continuously for most of the activity period except for occultation by the earth. In association with the 2B flare on August 4, 1972, and the 3B flare on August 7, 1972, the monitor provides evidence for solar gamma ray line emission in the energy range from 300 keV to 10 MeV. A summary of all the results available from preliminary analysis of the data will be given.

Chupp, E. L.↗
NASA NTRS1972

Solar gamma rays and neutron observations

The present status of knowledge concerning the impulsive and the continuous emission of solar gamma rays and neutrons is reviewed in the light of the recent solar activity in early August 1972. The gamma ray spectrometer on OSO-7 has observed the sun continuously for most of the activity period except for occultation by the earth. In association with the 2B flare on 4 August 1972 and the 3B flare on 7 August 1972, the monitor provides evidence for solar gamma ray line emission in the energy range from 300 keV to 10 MeV. A summary of all the results available from preliminary analysis of the data will be given. Significant improvements in future experiments can be made with more sensitive instruments and more extensive time coverage of the sun.

Chupp, E. L.↗
NASA NTRS1972

A gamma ray monitor for the OSO-7 spacecraft.

A NaI(T2) gamma ray spectrometer with a CsI(Na) charged particle and anti-Compton shield has been developed for the spacecraft. The spacecraft telemetry system employs a 800 Hz clock and reads data out on a basic 32-word (byte) Main Frame cycle. The data from the instrument include spectral data, X-ray data, and housekeeping data. The gamma ray pulses from the anode of the central detector flow through the front end electronics, where they are amplified by a charge sensitive preamplifier. The admission of the desired gamma ray into the data stream is controlled by a linear gate.

Higbie, P. R.↗