Recent advances in the CHIANTI project Enrico Landi Naval Research Laboratory

Requirements for a database In order to be suitable for the analysis of modern high-resolution spectra, atomic databases need to - be complete- no lines left behind - be accurate- plasma diagnostics must not be 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 databases 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 for - more than 220 ions - innershell transitions - dielectronic satellite lines Continuum emissivities for - free-free radiation - free-bound radiation - two-photon continuum The CHIANTI database can be used at any wavelength range, but it is optimized for the Angstrom range.

CHIANTI data are: In ASCII format Selected from the refereed literature (no unpublished data) Critically assessed and evaluated With references to original literature CHIANTI is completely transparent to the end user FREELY available on the web at (and 5 other sites) Fully documented through user guides CHIANTI also provides:a mailing list(I maintain it myself) assistance to users at:

Level population calculation Level populations and line intensities are calculated including: level excitation Electron-ion collisional excitation Proton-ion collisional excitation Photoexcitation by any ambient radiation Radiative cascades Ionization and recombination into excited levels Dielectronic recombination (for satellite lines) level de-excitation Spontaneous radiative decay Electron-ion collisional de-excitation Autoionization (for satellite lines) CHIANTI also allows the use of non-Maxwellian distributions of electron velocities

Basic assumptions in CHIANTI The plasma is optically thin no radiative transfer The plasma is in ionization equilibrium ionization and recombination rates will be part of Version 6 The plasma density is lower than cm -3 rise of metastable levels for which there are no collisional rates Stimulated emission is neglected

CHIANTI diffusion 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) RHESSI(X-rays) Solar-B(EUV,X-rays) STEREO(EUV) RESIK(X-rays) –Included in other spectral codes APEC/APED PintOfAle Arcetri Spectral Code XSTAR –Included in theoretical models (i.e. loop models, solar irradiance models etc) –Referenced in 720 papers (as of July 25, 2006)

Benchmarks of CHIANTI data CHIANTI predictions have been compared to several observed spectra to determine its completeness and accuracy: SERTS A(Young etal 1998) SOHO - CDS/NIS A(Landi et al. 2002a) SOHO -SUMER A(Landi et al. 2002b) RESIK A(Chifor et al. 2006) SMM - FCS7-18 A(Landi & Phillips 2006) These comparisons have: Shown overall excellent agreement Shown areas where improvement was needed – led to new CHIANTI versions Showed where new calculations were needed – triggered new atomic physics calculations

What’s in CHIANTI 5.2 The CHIANTI database has been recently greatly expanded. The main features of the current version (Version 5.2) are: Physical processes Ionization and recombination effects in level populations Non-Maxwellian distributions of electron velocity Photoexcitation from any user-defined ambient radiation field New data 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 Complete re-assessment of energy levels and line identifications New data for Fe IX, Fe XII, Fe XV (crucial for narrow-band EUV imagers) from the Iron Project Other data and new ions for EUV and UV lines Software More efficient software

New data for high-energy configurations in Fe XVII-XXIII We have made use of Flexible Atomic Code, calculations ( Landi & Gu 2006 ) of Energy levels Radiative transition rates Electron-ion 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 For n=3 configurations, resonances were included using the isolated-resonance approximation R-Matrix (from IP or other sources) where used in place of FAC results where available

FAC results were compared to existing R-Matrix calculations Agreement was satisfactory, except for Fe XIX and Fe XX, where data (collision strengths) from TIPbase presented strange features: Fe XIXFe XX FAC-DW TIPbase FAC-DW New calculations are needed for Fe XIX and XX

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 XVIII to XXIVinnershell transitions Fe II to Fe XXIVdielectronic satellite lines Si XII, S XVI, Ca XVIIIdielectronic 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

Effects of Ionization and Recombination on level populations 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 for Fe XVII to Fe XXIV He-like ions H-like ions Most 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 holds only up to a certain maximum density 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 He-like ions From >10 to > 15 H-like ions > 13 Corrections to intensities of observed lines are usually within a factor 2

Future CHIANTI features We are working on the next version of CHIANTI (Version 6), which will include: –Ionization and recombination rates – to allow studies of transient ionization; –New data for high-energy configurations in all isoelectronic sequences –to predict lines in X-ray and UV spectra; –New data for Fe ions from the Iron Project –to predict lines in the X-ray and EUV range; –New data for satellite lines –to account for all contributions; –More data for proton excitation rates

Benchmarking atomic data for X-ray lines Enrico Landi Naval Research Laboratory

Comparison with X-ray observations We have compared the new CHIANTI 5.2 with observations of two moderate solar flares InstrumentSMM/FCS SMM/FCS Date of observationAugust 25, 1980July 2, 1985 Wavelength ranges A A A A Spectral resolution1-20 mA1-5 mA SourceM 1.5 flareM 4.5 flare Spectral scan Duration17.5 minutes27 minutes Ions considered/availableFe XVII to Fe XXIIIFe XIX to Fe XXIV Ni XIX, Ni XX

Ion N. lines Aug.25 Jul.2 Fe XVII26- Fe XVIII40- Fe XIX433 Fe XX325 Fe XXI1113 Fe XXII418 Fe XXIII39 Fe XXIV-7 Ni XIX5- Ni XX5- Total16955 Lines/ions available

Comparison method-I FCS spectra were not observed simultaneously, so the flare plasmas were Divided in time bins All lines in the same time bin were analyzed together The plasmas in the two flares were analyzed by Landi & Phillips (2005) and found to be Isothermal within each time bin Slowly evolving with time (except at flare onset) The emission measure analysis was applied to each time bin in each spectrum

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 ratios must be the same at all temperatures, within the uncertainties. Comparison method-II

Example: Fe XIX – Aug.25 spectrum CHIANTI 4.2 CHIANTI 5 Time bin 1 Time bin 2

Results - I The Emission Measure allowed us to: Assess the quality of CHIANTI 5 data Identify blends from other ions evaluate the contribution of each component of a blend to the total intensity (additional check on atomic physics) Identify areas where improvements are still needed The two flare spectra allowed us to benchmark transitions from the following configurations: Aug 25:n=3Fe XVII to Fe XXIII n=4Fe XVII to Fe XIX Jul 2:n=4,5Fe XIX to XXIV

The comparison showed good agreement (171 lines out of 224): Fluxes of unblended lines were successfully reproduced Fluxes of blended lines were successfully reproduced once all contributions were considered A few more lines were identified A few lines (30 lines out of 224) had problems Fe XVIII, Fe XIX had problems in the A range (23 lines out of 224) Results - II

Results - III A few lines (30 lines out of 224) had problems: 6 lines had excess predicted flux –real atomic physics problems –mis-identification 24 lines had excess observed flux –real atomic physics problems –unidentified blends Lines with excess predicted flux: IonWvl.(A)Comment Fe XVII15.014Long standing problem Fe XIX,XX13.091Problem due to Fe XX Fe XVII,XIX10.655Possibly mis-identified with line at A Fe XXI9.587Weak line Fe XXII9.253 Fe XXIII8.304Difficult benchmark due to paucity of Fe XXIII lines

Results - IV Fe XVIII and Fe XIX had problems in the A range (23 lines out of 224) Lines of each ion could be separated in a few groups: Fe XVIII:group Agroup B Fe XIX:group Agroup Bgroup C The lines within groups showed a peculiar behaviour: Lines within each group agreed with each other Lines of different groups disagreed: –Fe XVIII:I A ~ 2 I B –Fe XIX:I A ~1.5 I B I A ~3.6 I C Characteristics of each group: Lines of different configurations belonged to the same group Lines of the same configuration belonged to different groups

Results - V The problem seems to exist also in other databases Possible causes: BlendingUnlikelyGroups too well defined Inaccurate wavefunctionsUnlikelyIncluded all configurations Missing resonancesPossibleNeed new calculations Satellite linesWork in progress After the comparison was done, new Iron Project calculations of Fe XVIII have been published (Witthoeft et al 2006) Differences are smaller, Iron Project data are a great improvement The “group pattern” has disappeared A few discrepancies are still present

Detailed processes: Fe XVII This comparison also allowed us to look with detail to each excitation process within each ion. We use as an 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 »R-Matrix rates including resonances for some of the lowest levels »Recombination into excited levels 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 predictions obtained with and without those processes

WITHOUT additional processes WITH additional processes A Still need some work on A All other lines are now OK

Results and Conclusions CHIANTI 5.2 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 5.2 represents a major advance over previous versions and other databases Work is needed for Fe XVIII and Fe XIX in the A range