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Delayed X- and Gamma-Ray Line Emission from Solar Flare Radioactivity

This study explores delayed line emissions and gamma-ray activity from solar flares, focusing on radioisotope production cross-sections, interaction models, and spectral analysis. Using experimental data and theoretical estimates, the research investigates the time-dependent emission patterns following solar flares. The study presents findings on various radioisotopes and their production yields, offering insights into the energy spectra and source compositions associated with solar activity. Additionally, the investigation includes detailed analysis of line emissions at specific energies and discusses the radioisotope enrichment implications derived from delayed gamma-ray measurements.

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Delayed X- and Gamma-Ray Line Emission from Solar Flare Radioactivity

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  1. Delayed X- and Gamma-Ray Line Emission from Solar Flare Radioactivity V. Tatischeff, B. Kozlovsky, J. Kiener and R. J. Murphy ApJS, submitted • Proposed by Ramaty & Mandzhavidze (2000, IAU Symp.) • size and development of the radioactive patch • mixing and transport processes in the solar atmosphere • the most promising delayed line is at 847 keV from 56Codecay

  2. Selection of the Radioisotopes • 10 min <T1/2 < 77 days • 21 b+-emitters (KLR87 + KMS04) + 7Be, 24Na, 56Mn, 58Com • Updated cross sections for the production of 34Clm, 52Mng, 52Mnm, 55Co, 56Co, 57Ni, 58Cog, 60Cu and61Cu by p, a and 3He reactions

  3. TALYS calculations Data: Michel et al. (1997) x10-2 x10-4 x10-6 Radioisotope Production Cross Sections • Experimental reaction data from EXFOR http://www.nndc.bnl.gov/exfor/ + Theoretical estimates from EMPIRE-II (version 2.19), TALYS (version 0.64), and the "Silberberg & Tsao" code above ~250 MeV (cosmic-ray physics)

  4. Radioisotope Production Yields • Thick target interaction model with nuclear destruction and catastrophic energy loss (e. g. pion production) of the fast ions (interactions between fast and ambient heavy ions are negligible) • Power law source spectrum up to 1 GeV/nucleon, with s=3.5, 2 and 5 • Impulsive-flare composition from SEP, with a/p=0.5 and 3He/a=0.5

  5. * Delayed line emission 30 min after the end of the flare • Unexpected strong lines at 1434 keV from 52Mnm, 1332 and 1792 keV from 60Cu, 6.92 (Co Ka) from 58Com (Ex=25 keV) + 57Ni, 2127 keV from 34Clm... • Normalized to a fluence of 300 g cm-2 emitted in the sum of the 4.4 and 6.1 MeV prompt narrow lines (2003 Oct. 28 flare)

  6. The experimental proof

  7. * Delayed line emission 3 h after the flare • The strongest line after that at 511 keV can be the neutral Co Ka line • Photoelectric attenuation: at solar depths of 10-3–10-1 g cm-2 (low chromosphere), the optical depths of 6.92 keV X-rays are ~ 10-3–10-1 • X-ray imaging of the radioactive patch ? • Normalized to a fluence of 300 g cm-2 emitted in the sum of the 4.4 and 6.1 MeV prompt narrow lines (2003 Oct. 28 flare)

  8. * Delayed line emission 3 days after the flare Time dependence of the 511 keV line • From ~1 to ~14 hours, the main source of the positrons is18F, which can be mainly produced by 16O(3He,p)18F • Measurement of the 511 keV decay curve can provide the accelerated 3He abundance

  9. Reames et al. (1994) H/4He ? 3He/4He Reames (1995) The influence of the accelerated ion composition • SEP composition for fast C and heavier elements relative to a-particles, but with a/p=0.5 ( a–a line in g-ray flares, SM97...) • Strong enhancement of the fast heavy elements, with e.g. AFe/Ap=137 nFe/nH • The delayed lines will measure this enrichment

  10. … an artist’s Cosmic Vision The Gamma-Ray Imager From J. Knödlseder, ESLAB Symposium 2005

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