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Element Abundance Results from CDS

Element Abundance Results from CDS. Dr Peter Young SOHO/CDS Project Scientist CCLRC Rutherford Appleton Laboratory. Why are abundances interesting?. Fractionation found to occur in corona and solar wind related to FIP of element magnitude depends on type of solar feature

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Element Abundance Results from CDS

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  1. Element Abundance Results from CDS Dr Peter Young SOHO/CDS Project Scientist CCLRC Rutherford Appleton Laboratory Dr Peter Young, CCLRC/RAL

  2. Why are abundances interesting? • Fractionation found to occur in corona and solar wind • related to FIP of element • magnitude depends on type of solar feature • Stellar X-ray spectra have revealed an inverse FIP effect in active stars • Photospheric abundances have been revised recently leading to problems for standard solar model Dr Peter Young, CCLRC/RAL

  3. The FIP effect • FIP - “First Ionization Potential” • Low-FIP (≤ 10 eV) elements enhanced relative to high-FIP elements in corona and solar wind • Factor varies relative to solar feature, e.g., • fast solar wind: 2 • slow solar wind: 4-5 • coronal structures: up to 10-15 Dr Peter Young, CCLRC/RAL

  4. Abundances with CDS • NIS covers two wide wavelength bands covering consecutive ion stages for several elements Dr Peter Young, CCLRC/RAL

  5. Abundance Methods • Simple method • find two ions formed at the same temperature • intensity ratio proportional to abundance ratio • Complicated method • use line intensities from many ions to create DEM • abundances varied to ‘improve’ fit Dr Peter Young, CCLRC/RAL

  6. Mg/Ne Abundance in Quiet Sun • Measurements of the FIP effect in the quiet Sun were difficult with previous instrumentation (Skylab) and SUMER • Isolated measurements using CDS performed by Del Zanna, Landi, MacPherson, Young • suggest FIP enhancement of 1 – 2 • AIM: perform definitive measurements of Mg/Ne ratio in quiet Sun regions over a 2 year period Dr Peter Young, CCLRC/RAL

  7. CDS observations • Quiet Sun spectral atlas (NISAT) every week of mission • 20” x 240” spatial area • Only consider regions away from bright points and ARs • Data from 1996 March to 1998 June Dr Peter Young, CCLRC/RAL

  8. Analysis procedure • Complete NIS spectra for supergranule cell centre and network regions extracted based on O V image • Emission lines of Ne IV-VII and Mg V-VIII identified and fit with Gaussian profiles Dr Peter Young, CCLRC/RAL

  9. Analysis procedure • Minimization procedure applied by specifying plasma column depths, d, over log T = [5.0,6.1], 0.1 intervals • d1, d2,d3 values at log T = 5.0, 5.6, 6.1 • Other values obtained by linear interpolation • CHIANTI/v4.2 used to compute line emissivities • Ab(Mg)/Ab(Ne), d1, d2,d3 are the 4 free parameters Dr Peter Young, CCLRC/RAL

  10. Abundance results Dr Peter Young, CCLRC/RAL

  11. Abundance results • Average enhancements over photospheric Mg/Ne value: • Network: 1.25 ± 0.10 • Cell centres: 1.66 ± 0.23 • Cell centres clearly show stronger enhancement • More details see Young (2005, A&A, 439, 361) Dr Peter Young, CCLRC/RAL

  12. Interpretation • Results consistent with cartoon of H. Peter (2001) • Small fraction of quiet Sun connects to solar wind • Closed quiet Sun loops show photospheric abundances Dr Peter Young, CCLRC/RAL

  13. Active regions • A striking feature of ARs are bright points with strongly enhanced transition region lines • One class of such brightenings have very strong Mg lines Dr Peter Young, CCLRC/RAL

  14. Emerging AR, June 1996 AR 7968 Dr Peter Young, CCLRC/RAL

  15. Emerging AR, June 1996 • Inner brightenings in region of flux emergence • Outer brightenings at base of large coronal loops Dr Peter Young, CCLRC/RAL

  16. Conclusions • Central brightenings show photospheric Mg/Ne ratio • Loop footpoints show factor 10 enhancement in Mg/Ne • More details see Young & Mason (1997, Sol. Phys., 175, 523) Dr Peter Young, CCLRC/RAL

  17. Future Work • General Mg/Ne results for ARs • Ne/O abundance • Minor elements: Ar, K, Ca Dr Peter Young, CCLRC/RAL

  18. General Mg/Ne results for ARs • Widing & Feldman (2001, ApJ) found magnitude of FIP effect related to age of active region using Skylab data • With CDS it should be possible to look at variation in individual AR structures Dr Peter Young, CCLRC/RAL

  19. General Mg/Ne results for ARs Dr Peter Young, CCLRC/RAL

  20. Ne/O relative abundance • Recent downward revisions of C, N, O & Ne abundances have caused problems for standard solar model • Drake & Testa (2005, Nature) suggested solar Ne/O ratio is in error Dr Peter Young, CCLRC/RAL

  21. Ne/O relative abundance • Including oxygen in the quiet Sun Mg/Ne analysis: QS network Drake & Testa photospheric Dr Peter Young, CCLRC/RAL

  22. Minor Elements: K, Ar, Ca • Potassium • K VIII λ519.4, K IX λ621.4 • Argon • Ar VII λ585.8 • Calcium • Ca VII λ551.4, Ca VIII λ596.9, Ca X λ557.7 Dr Peter Young, CCLRC/RAL

  23. Future Missions • Solar-B/EIS • ideal for coronal abundances • Fe/S, Ar/Ca • Solar Orbiter • high spatial resolution for studying individual structures • Ne/Ca? Dr Peter Young, CCLRC/RAL

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