skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Accelerated Particle Properties in Solar Flares from Gamma-Ray Line Observations

Abstract

In solar flares with strong {gamma}-ray emission, several prominent narrow lines can usually be observed emerging from a broad structure in the several hundred keV to several MeV region. They are produced by interactions of energetic protons, 3He and {alpha}-particles with the most abundant isotopes in the solar atmosphere. The underlying continuum is due to electron and positron bremsstrahlung and to the superposition of broad lines from accelerated heavy ions as well as numerous narrow nuclear lines which are too weak to be resolved individually. The properties of the accelerated particles in the October 28, 2003 flare observed with the gamma-ray spectrometer SPI onboard INTEGRAL were deduced by comparison of prominent narrow line fluence ratios, the line shapes of the 4.4 MeV 12C and 6.1 MeV 16O lines and the total nuclear line emission in the framework of a thick target interaction model.

Authors:
;  [1];  [2];  [3];  [4]
  1. CSNSM, IN2P3-CNRS and Univ Paris-Sud, 91405 Campus Orsay (France)
  2. Centre d'Etude Spatiale des Rayonnements, 9 av. du Colonel Roche, 31028 Toulouse (France)
  3. DSM/DAPNIA/Service d'Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette (France)
  4. USTHB, Faculte de Physique, BP 32, El Alia, 16111 Bab Ezzouar, Algiers (Algeria)
Publication Date:
OSTI Identifier:
21056748
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 891; Journal Issue: 1; Conference: 6. Symposium on nuclear physics, Tours (France), 5-8 Sep 2006; Other Information: DOI: 10.1063/1.2713525; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ALPHA REACTIONS; BREMSSTRAHLUNG; CARBON 12; COMPARATIVE EVALUATIONS; ELECTRONS; ELEMENT ABUNDANCE; GAMMA DETECTION; GAMMA SPECTROSCOPY; HEAVY ION REACTIONS; HEAVY IONS; HELIUM 3 REACTIONS; KEV RANGE; MEV RANGE; OXYGEN 16; PHOTON EMISSION; POSITRONS; PROTON REACTIONS; PROTONS; SOLAR ATMOSPHERE; SOLAR FLARES

Citation Formats

Kiener, J., Tatischeff, V., Weidenspointner, G., Gros, M., and Belhout, A.. Accelerated Particle Properties in Solar Flares from Gamma-Ray Line Observations. United States: N. p., 2007. Web. doi:10.1063/1.2713525.
Kiener, J., Tatischeff, V., Weidenspointner, G., Gros, M., & Belhout, A.. Accelerated Particle Properties in Solar Flares from Gamma-Ray Line Observations. United States. doi:10.1063/1.2713525.
Kiener, J., Tatischeff, V., Weidenspointner, G., Gros, M., and Belhout, A.. Mon . "Accelerated Particle Properties in Solar Flares from Gamma-Ray Line Observations". United States. doi:10.1063/1.2713525.
@article{osti_21056748,
title = {Accelerated Particle Properties in Solar Flares from Gamma-Ray Line Observations},
author = {Kiener, J. and Tatischeff, V. and Weidenspointner, G. and Gros, M. and Belhout, A.},
abstractNote = {In solar flares with strong {gamma}-ray emission, several prominent narrow lines can usually be observed emerging from a broad structure in the several hundred keV to several MeV region. They are produced by interactions of energetic protons, 3He and {alpha}-particles with the most abundant isotopes in the solar atmosphere. The underlying continuum is due to electron and positron bremsstrahlung and to the superposition of broad lines from accelerated heavy ions as well as numerous narrow nuclear lines which are too weak to be resolved individually. The properties of the accelerated particles in the October 28, 2003 flare observed with the gamma-ray spectrometer SPI onboard INTEGRAL were deduced by comparison of prominent narrow line fluence ratios, the line shapes of the 4.4 MeV 12C and 6.1 MeV 16O lines and the total nuclear line emission in the framework of a thick target interaction model.},
doi = {10.1063/1.2713525},
journal = {AIP Conference Proceedings},
number = 1,
volume = 891,
place = {United States},
year = {Mon Feb 26 00:00:00 EST 2007},
month = {Mon Feb 26 00:00:00 EST 2007}
}
  • Analyses of gamma-ray line emission in solar flares have provided information about conditions in flaring magnetic loops, the abundances of the chromosphere where the gamma rays are produced, and the composition and spectrum of the flare-accelerated ions. While laboratory measurements of the cross sections for production of the strongest lines seen in flare spectra are available, these measurements often only cover a limited range of projectile energies. In addition, the bulk of the gamma-ray emission arises from the numerous weaker lines for which there are no measurements. The gamma-ray de-excitation-line production code, developed originally by Ramaty, Kozlovsky, and Lingenfelter, hasmore » been and continues to be the primary theoretical tool used for analyses of solar-flare gamma-ray data. The code uses both measured cross sections and estimated cross sections where measurements are inadequate. We have improved the completeness and accuracy of this code in three ways. (1) We use recent cross section measurements to improve cross sections for those lines already explicitly included in the code and to provide cross sections for new explicit lines. (2) For the first time, we give a detailed evaluation of the unresolved-line 'continuum' (i.e., all line emission not accounted for by the explicit lines in the code). Because adequate laboratory measurements for this emission are not available, the primary tool for this evaluation was the theoretical nuclear program TALYS. We explore how this unresolved-line continuum depends on parameters relevant for solar flares. (3) We use TALYS to improve those line cross sections where available laboratory measurements are inadequate and to provide cross sections for new explicit lines for which no measurements exist. Numerical cross section values for all lines explicitly addressed by the code and for the unresolved-line continua are given in the Appendix.« less
  • Anisotropies of charged particles accelerated in solar flares can be studied by observing Doppler shifts of selected $gamma$-ray lines. The spectral shape of the 6.1 MeV line of $sup 16$O has been calculated. If the accelerated particles are isotropic, the line remains centered at E$sub 0$=6129.4 keV, and its width (FWHM) is about 100 keV. However, for particle anisotropies that may be produced in solar flares, the line is shifted to lower energies by about 30 to 40 keV. (AIP)
  • Gamma-ray spectroscopy provides diagnostics of particle acceleration in solar flares, but care must be taken when interpreting the spectra due to effects of the angular distribution of the accelerated particles (such as relativistic beaming) and Compton reprocessing of the radiation in the solar atmosphere. In this paper, we use the GEANT4 Monte Carlo package to simulate the interactions of accelerated electrons and protons and study the effects of these interactions on the gamma rays resulting from electron bremsstrahlung and pion decay. We consider the ratio of the 511 keV annihilation-line flux to the continuum at 200 keV and in themore » energy band just above the nuclear de-excitation lines (8-15 MeV) as a diagnostic of the accelerated particles and a point of comparison with data from the X17 flare of 2003 October 28. We also find that pion secondaries from accelerated protons produce a positron annihilation line component at a depth of {approx}10 g cm{sup -2} and that the subsequent Compton scattering of the 511 keV photons produces a continuum that can mimic the spectrum expected from the 3{gamma} decay of orthopositronium.« less
  • The profiles of 0.429 and 0.478 MeV gamma-ray lines from Be-7 and Li-7 (produced by interactions of flare-accelerated alpha particles with ambient He in the solar atmosphere) and of the 4.438 MeV line from C-12 (produced by inelastic scattering of C-12 by accelerated protons) depend on the angular distribution of the interacting accelerated particles. The line profiles resulting from various assumed accelerated-particle angular distributions are calculated and it is shown that it will be possible to distinguish among them using observations of gamma-ray spectra from solar flares obtained with high resolution detectors. 28 references.
  • We review the evidence for the existence of two distinct classes of solar accelerated particles; we present new results on abundances from gamma-ray spectroscopy and on electron energy spectra; and we discuss the implications of comparisons of particle and gamma-ray observations.