Characterizing Thermal and Non- Thermal Electron Populations in Solar Flares Using RHESSI Amir Caspi...
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Characterizing Thermal and Non-Thermal Electron Populations in Solar Flares Using RHESSI Amir Caspi 1,2 , Säm Krucker 2 , Robert P. Lin 1,2 1 Department of Physics, University of California, Berkeley, CA 94720 2 Space Sciences Laboratory, University of California, Berkeley, CA 94720
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Transcript of Characterizing Thermal and Non- Thermal Electron Populations in Solar Flares Using RHESSI Amir Caspi...
Characterizing Thermal and Non-Thermal Electron Populations in
Solar Flares Using RHESSI
Amir Caspi1,2, Säm Krucker2, Robert P. Lin1,2
1 Department of Physics, University of California, Berkeley, CA 947202 Space Sciences Laboratory, University of California, Berkeley, CA 94720
June 3, 2004 AAS/SPD Meeting 2
Motivation
June 3, 2004 AAS/SPD Meeting 3
Questions
• Is the flare isothermal?– If not, what is the temperature distribution?– Where are thermal sources located?
• What is the low-energy cutoff for the nonthermal emission?– Critical for energy estimates
Want to determine flare energetics, heating and acceleration mechanisms
June 3, 2004 AAS/SPD Meeting 4
Fe & Fe/Ni line complexes
• Line(s) are visible in almost all RHESSI flare spectra• Fluxes and equivalent width of lines are strongly
temperature-dependent (Phillips 2004)
June 3, 2004 AAS/SPD Meeting 5
Fe & Fe/Ni line complexes
• Differing temperature profiles of line complexes suggests ratio is unique determination of isothermal temperature (Phillips 2004)
June 3, 2004 AAS/SPD Meeting 6
Fe & Fe/Ni line complexes
• Assume isothermal– Not necessarily the
best fit!
• Single power law with low-energy cutoff
• 2 Gaussians to approximate Fe & Fe/Ni line complexes
June 3, 2004 AAS/SPD Meeting 7
Flux ratio vs. Temperature
June 3, 2004 AAS/SPD Meeting 8
Flux ratio vs. Temperature
June 3, 2004 AAS/SPD Meeting 9
Flux ratio vs. Temperature
June 3, 2004 AAS/SPD Meeting 10
Flux ratio vs. Temperature
June 3, 2004 AAS/SPD Meeting 11
Flux ratio vs. Temperature
June 3, 2004 AAS/SPD Meeting 12
More questions
• Well-defined correlation between Fe to Fe/Ni ratio and isothermal temperature for each flare, but…
• No agreement between observations and theory
• No agreement between individual flares!
• Why are observations so far from the theory?
• Why are the curves different between flares?
June 3, 2004 AAS/SPD Meeting 13
Possible answer
• Multi-thermal distribution– Differs between flares
• Imaging spectroscopy would be ideal– Obtain spectra based on source location
• Isolate and analyze multiple thermal plasmas at different temperatures within each flare
• Distinguish between thermal and non-thermal sources
June 3, 2004 AAS/SPD Meeting 14
Centroids of emission
• Clear displacement between centroids of lower energy and higher energy emission
June 3, 2004 AAS/SPD Meeting 15
Centroids of emission
• Higher energy emission from higher in the looptop– Strongly implies multi-thermal distribution
• Centroid of Fe line complex emission consistent with high-EM, lower-T plasma lower in looptop
June 3, 2004 AAS/SPD Meeting 16
Conclusions• Observations do not agree with predictions
– Multi-thermal distribution
– Other variations
Ongoing Work• Obtain DEM to determine temperature distributions• Imaging spectroscopy for spatially-separated sources, to
separate thermal sources at different temperatures, and to distinguish between thermal and non-thermal sources
Determine flare energetics
June 3, 2004 AAS/SPD Meeting 17
Count Spectrum
June 3, 2004 AAS/SPD Meeting 18
Flux ratio vs. Temperature
June 3, 2004 AAS/SPD Meeting 19
Flux ratio vs. Temperature
June 3, 2004 AAS/SPD Meeting 20
Flare location/size
