SOLAR ENERGETIC ION AND ELECTRON LIMITS FROM HIREGS OBSERVATIONS

The HIgh-REsolution Gamma-ray and hard X-ray Spectrometer (HIREGS) consists of an actively shielded array of twelve liquid-nitrogen-cooled germanium detectors designed to provide unprecedented spectral resolution and narrow-line sensitivity for solar gamma-ray line observations. Two long-duration, c...

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Bibliographic Details
Published in:Solar physics 1997-04, Vol.171 (2), p.419-445
Main Authors: Feffer, P T, Lin, R P, Slassi-Sennou, S, McBride, S, Primbsch, J H, Zimmer, G, Pelling, R M, Pehl, R, Madden, N, Malone, D, Cork, C, Luke, P, Vedrenne, G, Cotin, F
Format: Article
Language:English
Subjects:
Arrays
Bursts
Density
Deposition
Electrons
Emissions
Energy
Flares
Gamma rays
Germanium
Heating
Ions
Solar physics
Studies
X-rays
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Summary:The HIgh-REsolution Gamma-ray and hard X-ray Spectrometer (HIREGS) consists of an actively shielded array of twelve liquid-nitrogen-cooled germanium detectors designed to provide unprecedented spectral resolution and narrow-line sensitivity for solar gamma-ray line observations. Two long-duration, circumpolar balloon flights of HIREGS in Antarctica (10-24 January, 1992 and 31 December, 1992-10 January, 1993) provided 90.9 and 20.4 hours of solar observations, respectively. During the observations, eleven soft X-ray bursts at C levels and above (largest M1.7) occurred, and three small solar hard X-ray bursts were detected by the Compton Gamma-Ray Observatory. HIREGS detected a significant increase above 30 keV in one. No solar gamma-ray line emission was detected. Limits on the 2.223-MeV line and the hard X-ray emission are used to estimate the relative contribution of protons and electrons to the energy in flares, and to coronal heating. For the 2.223-MeV line, the upper limit fluence is 0.8 ph cm super(-2) in the flares, and the upper limit flux is 1.8 10 super(-4) ph s super(-1) cm super(-2) in the absence of flares. These limits imply that 6 10 super(30) (2s) protons above 30 MeV were accelerated in the flares, assuming standard photospheric abundances and a thick target model. The total energy contained in the accelerated protons >30 MeV is 4 10 super(26) ergs, but this limit can be more than 10 super(30) ergs if the spectrum extends down to 1 MeV. The upper limit on the total energy in accelerated electrons during the observed flares can also exceed 10 super(30) ergs if the spectrum goes down to 7 keV. Quiet-Sun observations indicate that 10 super(26)erg s super(-1) are deposited by energetic protons >1 MeV, well below the10 super(27) -10 super(28) erg s super(-1) required for coronal heating, while
ISSN:0038-0938
1573-093X
DOI:10.1023/A:1004911511905