Probing Ion Acceleration by Observing Gamma Rays
from Solar FlaresAlbert Y. Shih1
NASA Advisor: Brian R. Dennis2
Faculty Advisor: Robert P. Lin1
1 Department of Physics and Space Sciences Laboratory, UC Berkeley, Berkeley, CA2 4 NASA Goddard Space Flight Center, Greenbelt, MD
Flare
electrons
protons, alphas, heavy ions
neutrons
bremsstrahlung
nuclear de-excitation, positron annihilation
neutron-capture Sun
Gamma rays
Thermalizationtime delay of ~ 100 secondsspatial separation of < 1 arcsec
n (cm-3)
1011
1012
1013
1014
1015
A RHESSI gamma-ray spectrum
Model components
positron annihilation
neutron-capture
bremsstrahlung
nuclearde-excitation
total model
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.
Temporal Variability Analysis00:27:20–00:32:56 UT 00:32:56–00:43:20 UT
Low-FIP: Fe , Mg , Si
High-FIP: Ne , C , O
Temporal Variability Results2002 July 23 2003 October 28 2003 November 2
0.29±0.08 0.80±0.14
Low-FIP/high-FIP ratiosLow-FIP/high-FIP ratios
0.36±0.05 0.74±0.20
Protons vs. thermal emission
Region not fully investigated
Protons vs. high-energy electrons
Direct proportionality
After selection cuts
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