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Cristina Chifor SESI Student Intern 2005 Solar Physics, Code 612 NASA/Goddard Space Flight Center

FE AND FE/NI SPECTRAL LINE COMPLEXES IN RHESSI SOFT X-RAYS. Cristina Chifor SESI Student Intern 2005 Solar Physics, Code 612 NASA/Goddard Space Flight Center Mentors: Dr. Ken Phillips & Dr. Brian Dennis. SOLAR FLARE X-RAYS. 2. Thermal Depends on the random thermal

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Cristina Chifor SESI Student Intern 2005 Solar Physics, Code 612 NASA/Goddard Space Flight Center

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  1. FE AND FE/NI SPECTRAL LINE COMPLEXES IN RHESSI SOFT X-RAYS Cristina Chifor SESI Student Intern 2005 Solar Physics, Code 612 NASA/Goddard Space Flight Center Mentors: Dr. Ken Phillips & Dr. Brian Dennis

  2. SOLAR FLARE X-RAYS 2. Thermal • Depends on the random thermal motion of the heated electrons • Maxwellian distribution of electron velocities 1. Non-Thermal • Synchrotron radiation • Electron kinetic energy higher than average thermal energy of plasma BREMSSTRAHLUNG ELECTRON PROTON PHOTON

  3. REUVEN RAMATY HIGH ENERGY SOLAR SPECTROSCOPIC IMAGER • X-ray/gamma-ray spectrometer : 3 keV – 17 MeV • 9 Ge detectors • ~ 1 keV resolution • Images through modulation collimators (~2 arcsec resolution) • Movable shutters control high photon fluxes

  4. SPECTRAL MODELLING “One spectrum is worth a thousand images”…. A. Dupree. • Thermal component of flare X-rays ( 3 keV -20 keV ) • Physical plasma properties: T, emission measure, elemental abundances etc.

  5. MAIN PROJECT GOAL : Whybother ? • Valuable diagnostic information about emitting plasma (e.g. T dependent) • Can determine the origin of flare plasma (since coronal Fe abundances ~ 4 x photospheric Fe abundances) • Better understand the RHESSI transmission as a function of energy in different attenuator states and the effects of increased count rates Analyze the Fe (~6.7 keV) and Fe/Ni (~8 keV) line complexes in the soft X-ray part of the solar flare spectra from RHESSI.

  6. FLARE SAMPLING Using the Geostationary Operational Environmental Satellites (GOES). • Isothermal approximation OK in the late decay stages • So, hunt for long duration, slowly decaying flares • IDL GUI to make quick plots of monthly GOES data • Any RHESSI data for the selected times (no data gaps, particle precipitation events, SAA) ?

  7. METHOD 1. Count rate spectrum file + response matrix file • 20 - 60 s time bins • 0.3 keV energy bins • 2. Background subtraction • Choose model functions to fit ~ 5 – 15 keV • Fit model to data: • 1 isothermal component + 2 Gaussian lines (1 keV FWHM) centered at ~ 6.7 and 8 keV • Reduce chi-squared 5. Calculate complexes EQW + plot vs. T In total, this summer: > 2000 spectra for > 30 flares

  8. THE BULK OF RESULTS: http://hesperia.gsfc.nasa.gov/hessi/chifor

  9. COMPLICATIONS : MULTI-THERMAL FLARE PLASMAS • Most evident during flare rise, peak, soon after peak. • Each T component in a multi-thermal plasma contribute to the fluxes in the Fe and Fe/Ni complexes To help with DEM analysis, we had guests this summer ! • Dr. Janusz Sylwester (Polish Academy of Sciences) • RESIK (soft X-ray Bragg crystal spectrometer) • DEM – onology • RESIK vs RHESSI cross-calibrations • LiWei Lin (Harvard – Smithsonian Astrophysical Observatory) • Pint Of Ale

  10. MORE COMPLICATIONS: INSTRUMENTAL High count rates in RHESSI detectors decrease energy resolution in the soft X-ray range and increase calculated T. • Line complexes difficult to detect. Fitting Gaussians vary in width. • Does this mean that results from lowest count rates (both sets of shutters in ) are most reliable ? • http://hesperia.gsfc.nasa.gov/hessi/chifor/may072002_html/feqw.htm • http://hesperia.gsfc.nasa.gov/hessi/chifor/nov112003_html/nov112003.htm

  11. CONCLUSIONS RHESSI instrumental effects are important (e.g. high count rates decrease energy resolution in the soft X-ray range). Multi – thermal flare plasma calls for DEM techniques. However, ok results where isothermal approximation appropriate. Coronal origin of flare plasma (from calculated Fe abundances). Fe and Fe/Ni EQWs vs. T follow theoretical diagnostic curves. But, there may be a need for improved theoretical atomic calculations. “RHESSI Observations of the Solar Flare Fe and Fe/Ni Lines” : paper to be submitted to the Astrophysical Journal soon.

  12. SPECIAL THANK YOU: Dr. Ken Phillips Dr. Brian Dennis Ana Rosas Merrick Berg CUA International Office

  13. END OF PRESENTATION

  14. Count rate spectral fit in OSPEX

  15. RHESSI count flux vs. time

  16. Ingredients % by number of atoms % by mass Hydrogen - H 92.0 73.4 Helium - He 7.8 25.0 Oxygen - O 0.06 0.8 Carbon - C 0.03 0.3 Nitrogen - N 0.009 0.1 Neon - Ne 0.008 0.1 Silicon - Si 0.004 0.07 Iron - Fe 0.003 0.2 Magnesium - Mg  0.003 0.07 Sulfur - S 0.002 0.04 Argon - Ar 0.0008 0.032 Aluminum - Al 0.00025 0.007 Calcium - Ca 0.00021 0.008 Sodium - Na 0.00020 0.005 Nickel - Ni 0.00020 0.012 SUN RECIPE

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