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Recent advances in the CHIANTI database in the X-ray range

Recent advances in the CHIANTI database in the X-ray range. Enrico Landi. Naval Research Laboratory. Overview. Introduction What is CHIANTI New features of the CHIANTI database Comparison with X-ray observations Conclusions. Introduction.

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Recent advances in the CHIANTI database in the X-ray range

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  1. Recent advances in the CHIANTI database in the X-ray range Enrico Landi Naval Research Laboratory

  2. Overview • Introduction • What is CHIANTI • New features of the CHIANTI database • Comparison with X-ray observations • Conclusions

  3. Introduction • X-ray spectra are of primary importance for quantitative studies of the physics of many astrophysical objects • Emission and absorption of line and continuum radiation in the X-rays offer a wide variety of diagnostic tools to determine the physical properties of emitting sources • For this reason, in the recent past, several instruments have been flown to observe astrophysical sources in the X-ray range: • Chandra ROSAT • XMM Yohkoh • RHESSI SMM • RESIK …and many others

  4. Why a database? • X-ray spectra are composed by line and continuum radiation, emitted by highly charged ions. • Observed X-ray spectral lines come from Rydberg series in the H-,He-like sequences High-energy configurations (n>2) in highly charged Fe and Ni ions Innershell transitions Dielectronic satellite lines • Continuum radiation comes from Free-free radiation Free-bound radiation

  5. In order to study this radiation and use it for plasma diagnostic purposes, a large amount of atomic data are needed for both line and continuum radiation • To address this need, several databases have been created in the past: CHIANTI MEKAL APEC/APED ADAS Arcetri Spectral Code

  6. Requirements for a database • In order to be suitable for the analysis of modern high-resolution spectra, atomic data bases need to -be complete no lines left behind - be accurate plasma diagnostics not hindered by atomic physics uncertainties - be easy-to-use - be transparent - the user can independently check the original data and their accuracy - no black box - all data independently refereed in peer reviewed literature • Also, atomic data and predicted emissivities from data bases need to be benchmarked against observations

  7. The CHIANTI database • CHIANTI consists of A database of atomic data and transition rates A suite of IDL programs for plasma diagnostics • CHIANTI is able to calculate Line emissivities formore than 230 ions innershell transitions dielectronic satellite lines Continuum emissivities forfree-free radiation free-bound radiation two-photon continuum Under the optically thin plasma assumption

  8. CHIANTI data are: • In ASCII format • Selected from the refereed literature (no unpublished data) • With references to original literature CHIANTI is completely transparent to the end user • FREELY available on the web at http://wwwsolar.nrl.navy.mil/chianti.html • Fully documented through user guides CHIANTI also maintains: a mailing list email assistance to users at: chianti_help@halcyon.nrl.navy.mil

  9. CHIANTIhas enjoyed great success in the astrophysical community. CHIANTI data have been • Included in the software of several satellite borne missions SOHO/CDS (EUV) SOHO/EIT (EUV) TRACE (UV) Solar-B (EUV,X-rays) STEREO (EUV) RHESSI (X-rays) • Included in other spectral codes APEC/APED PintOfAle Arcetri Spectral Code ADAS

  10. State-of-the-art • Literature data for the X-rays have several limitations: Missing configurations (n>3 in many Fe ions) Limited atomic models for n=3 configurations (usually due to computer memory limitation in the past) Missing processes: resonances ionization effects on level populations recombination effects on level populations cascades from higher levels Uncertainties in line identifications

  11. CHIANTI 5.0 • The CHIANTI database has been recently greatly expanded. The main features of the next CHIANTI release (Version 5.0) are: • New data for high-energy configurations in Fe XVII-XXIII n=3,4,5,6,7 Fe XVII n=3,4,5 Fe XVIII-XXIII • New data for satellite lines • Ionization and recombination effects in level populations • Complete re-assessment of energy levels and line identifications • Other data and new ions for EUV and UV lines

  12. New data for high-energy configurations in Fe XVII-XXIII • We have made use of the Flexible Atomic Code, by Dr. M.F. Gu, to calculate Energy levels Radiative transition rates Collisional transition rates (including resonances) for all configurations with n=3,4,5,6,7 Fe XVII n=3,4,5 Fe XVIII-XXIII • These data allow to predict lines in the 7-12 Angstrom range • Few if any data were available in the literature for most of these configurations • Data will be published separately (Landi & Gu 2005)

  13. New data for satellite lines • New data have been added to CHIANTI 5.0 for dielectronic satellite lines and innershell transitions, to match observations Fe XXIIIinnershell transitions S XVI, Ca XVIII, Fe XXIVdielectronic satellite lines • These new lines also provide diagnostic tools for measuring the plasma electron temperature • These lines allow to study RHESSI spectra in the 6-9 keV energy range

  14. Fe XXV Fe XXV Fe XXV Fe XXIV satellites Fe XXIV satellites Fe XXIV satellites

  15. Ionization and Recombination • Recently, Behar & Doron (2002) and Gu (2003) demonstrated that ionization and recombination are important contributors to steady-state level population in highly ionized Fe ions • CHIANTI 5.0 incorporates data and software to take these two processes into account • All recombination and ionization data have been taken from the Flexible Atomic Code calculations by Gu (2003).

  16. We make use of the Coronal Model Approximation: Without Ionization/Recombination: With Ionization/Recombination: Where: nq-1, nq, nq+1ion fractions CI, RECtotal ion. and rec. rates Egitotal excitation rate level i Digtotal de-excitation rate level i

  17. The Coronal Model Approximation is not valid if metastable levels have non-negligible population • As the electron density increases, the population of metastable levels in highly ionized Fe ions also increases • The maximum density at which metastable level populations are negligible changes from ion to ion: Ion Log Ne(max) Fe XVII any Fe XVIII > 13 Fe XIX 12 Fe XX 12 Fe XXI 12 Fe XXII 13 Fe XXIII > 13 Fe XXIV any

  18. Fe XVIII Fe XVII Fe XX Fe XIX

  19. Fe XXI Fe XXII Fe XXIII Fe XXIV

  20. Comparison with X-ray observations • We have compared the new CHIANTI 5.0 with observations of a moderate solar flare Instrument SMM/FCS (Bragg crystal spectrometer) Date of observation August 25, 1980 Wavelength ranges 13.1-22.4 A (channel 1) 10.6-14.9 A (channel 2) 7.3-10.1 A (channel 3) Spectral resolution 1-20 mA (depending on the channel) Source M 1.5 flare Spectral scan Duration 17.5 minutes Ions observed H-like O,Ne,Mg He-like O,Ne,Na,Mg,Al Fe ions Fe XVII to Fe XXIII Ni ions Ni XIX, Ni XX

  21. Comparison method • FCS spectra were not observed simultaneously, so the flare plasma was analyzed as a function of time • The Emission Measure analysis showed that • The flare plasma was isothermal • The temperature was decreasing slowly • The emission measure decreased by a factor 6 during the observation • This allowed us to use the Emission Measure as a tool to compare CHIANTI 5 emissivities and observed fluxes for each ion, to: • Assess the quality of CHIANTI 5 data • Identify blends from other ions and evaluate their contribution to the total intensity (additional check on atomic physics) • Identify areas where improvements are still needed

  22. In case of isothermal plasma • We can define, for all the lines of the same ion, the ratio • If there are no blends and no atomic physics problems, all the ratios must be the same at all temperatures, within the uncertainties.

  23. Example: Fe XIX CHIANTI 5 CHIANTI 4.2 Time bin 1 Time bin 2

  24. Example: Fe XVII • Long standing problems: • Strong 15.01 A line lower than predicted • Resonant scattering? • Satellites in 15.01/15.26 intensity ratios? • Disagreement in 2p-3s/2p-3d ratios • Innershell ionization to 3s? • Satellite contributions to line ratios? • Existing atomic data • DW collision rates from many authors • Only very recently resonance data have been considered • Doron & Behar (2002) showed that recombination is important for Fe XVII

  25. We used CHIANTI 5.0 to check the importance of many additional processes in Fe XVII level population: Process Importance CascadesModerate Collisional ionizationModerate RecombinationCrucial ResonancesCrucial • We have compared the FCS spectrum with CHIANTI 5.0 predictions obtained withand without those processes

  26. CHIANTI 4.2 15.01 A CHIANTI 5.0 15.01 A

  27. Results and Conclusions • CHIANTI 5.0 reproduces observed high- and low- resolution X-ray spectra with great accuracy All relevant configurations in Fe ions are now included Blending from ions of different species is accounted for Most lines are reproduced within 30% • CHIANTI 5.0 represents a major advance over previous versions and other databases • New diagnostic tools are now available to measure the physical properties of the emitting plasmas

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