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

Overview 1.Introduction 2.What is CHIANTI 3.New features of the CHIANTI database 4.Comparison with X-ray observations 5.Conclusions

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: ChandraROSAT XMMYohkoh RHESSISMM RESIK…and many others

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

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

Requirements for a database In order to be suitable for the analysis of modern high-resolution spectra, atomic data bases need to - be completeno lines left behind - be accurateplasma 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

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

CHIANTI data are: In ASCII format Selected from the refereed literature (no unpublished data) With references to original literature CHIANTI is completely transparent to the end user FREELY available on the web at Fully documented through user guides CHIANTI also maintains:a mailing list assistance to users at:

CHIANTI has 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

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

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=3,4,5,6,7Fe XVII n=3,4,5Fe 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

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=3,4,5,6,7Fe XVII n=3,4,5Fe 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)

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

Fe XXV Fe XXIV satellites Fe XXIV satellites Fe XXIV satellites

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).

We make use of the Coronal Model Approximation: Without Ionization/Recombination: With Ionization/Recombination: Where:n q-1, n q, n q+1 ion fractions CI, REC total ion. and rec. rates E gi total excitation rate level i D ig total de-excitation rate level i

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

Fe XVII Fe XVIII Fe XIX Fe XX

Fe XXIFe XXII Fe XXIVFe XXIII

Comparison with X-ray observations We have compared the new CHIANTI 5.0 with observations of a moderate solar flare InstrumentSMM/FCS (Bragg crystal spectrometer) Date of observationAugust 25, 1980 Wavelength ranges A (channel 1) A (channel 2) A (channel 3) Spectral resolution1-20 mA (depending on the channel) SourceM 1.5 flare Spectral scan Duration17.5 minutes Ions observedH-likeO,Ne,Mg He-likeO,Ne,Na,Mg,Al Fe ionsFe XVII to Fe XXIII Ni ionsNi XIX, Ni XX

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

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.

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

Example: Fe XVII Long standing problems: Strong 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

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

CHIANTI 4.2 CHIANTI A

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