1. Temporal Variability of Gamma- Ray Lines from the X-Class Solar Flare of 2002 July 23 Albert Y. Shih 1,2, D. M. Smith 1, R. P. Lin 1,2, S. Krucker 1, R. A. Schwartz 3, G. H. Share 4, R. J. Murphy 4 1 Space Sciences Laboratory, University of California, Berkeley, Berkeley, CA 2 Department of Physics, University of California, Berkeley, Berkeley, CA 3 NASA Goddard Space Flight Center, Greenbelt, MD 4 E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, D.C.

2. Flare p nd e+e+ e-e- , p, ions , p, ions  p Nuclear de-excitation Positron annihilation 0.511 MeV Neutron capture 2.223 MeV Solar Gamma Rays

3. Instrumentation Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) Spectrometer with germanium detectors

4. X-Class Flare of 2002 July 23 00:27:20–00:43:20 UT GOES X4.8 Location: S13E72 100-300 keV

5. Data Analysis Background subtraction: +/– 15 orbits Spectral Executive (SPEX) package Parameters of the fit: –Broken power law representing electron bremsstrahlung –Positron annihilation line (0.511 MeV) –Neutron capture line (2.223 MeV) –Narrow nuclear lines: Fe, Mg, Ne, Si, C, O –Broad Gaussians representing heavy ion interactions Error bars are obtained by determining the required change in each flux to increase the best-fit  2 by 1

6. Nuclear De-excitation Lines 00:32:56–00:43:20 UT 00:27:20–00:32:56 UT

7. Nuclear De-excitation Lines 00:32:56–00:43:20 UT 00:27:20–00:32:56 UT

8. Line Flux Variations

9. FIP (eV) Mg7.6 Low Fe7.9 Si8.2 C11.3 High O13.6 Ne21.6

10. Modeling Models –Decreasing  /proton ratio –Increasing spectral index –Low-FIP enhancement Other considerations –Change in interaction region (Murphy et al. 1997) –Enhancement of Ne (Murphy et al. 1991) –Multiple sources? x/TotalFit  /p  ss FIP Fe Mg Ne Si C O DecreaseIncrease

11. Conclusions In the flare on 2002 July 23, the evolution of the nuclear de-excitation line fluxes differs depending on the element This evolution does not agree well with the evolution predicted by several models Observations of gamma rays from future flares are eagerly awaited