1. Probing Ion Acceleration by Observing Gamma Rays from Solar Flares Albert Y. Shih 1 NASA Advisor: Brian R. Dennis 2 Faculty Advisor: Robert P. Lin 1 1 Department of Physics and Space Sciences Laboratory, UC Berkeley, Berkeley, CA 2 4 NASA Goddard Space Flight Center, Greenbelt, MD

2. Flare electrons protons, alphas, heavy ions neutrons bremsstrahlung nuclear de-excitation, positron annihilation neutron-capture Sun Gamma rays Thermalization time delay of ~ 100 seconds spatial separation of < 1 arcsec n (cm -3 ) 10 11 10 12 10 13 10 14 10 15

4. A RHESSI gamma-ray spectrum

5. Model components positron annihilation neutron-capture bremsstrahlung nuclear de-excitation total model

6. What can be done? Line energies –Angular distribution of accelerated ions Line fluxes –Ambient elemental abundances –Shape of the acceleration spectrum Line shapes –Accelerated elemental abundances –Temperature, density, etc.

7. Temporal Variability Analysis 00:27:20–00:32:56 UT00:32:56–00:43:20 UT

8. Low-FIP: Fe, Mg, Si High-FIP: Ne, C, O Temporal Variability Results 2002 July 232003 October 282003 November 2 0.29±0.080.80±0.14 Low-FIP/high-FIP ratios 0.36±0.050.74±0.20

9. Protons vs. thermal emission Region not fully investigated

10. Protons vs. high-energy electrons Direct proportionality After selection cuts

11. Future Work Modeling work to explore the scientific implications of these observations Searches for radioactive material persisting after flares Designs for future instruments to extend the observations of the signatures of ion acceleration to both lower and higher energies