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 ofA 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 1-2000 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• In ASCII format• Selected from the refereed literature (no unpublished data)• Critically assessed and evaluated• With references to original literature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

http://wwwsolar.nrl.navy.mil/chianti.html (and 5 other sites)

• Fully documented through user guides

CHIANTI also provides: a mailing list (I maintain it myself)

email assistance to users at: chianti_help@halcyon.nrl.navy.mil

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 1015 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 1989 170-450 A (Young etal 1998)

• SOHO - CDS/NIS 308-630 A (Landi et al. 2002a)

• SOHO -SUMER 500-1600 A (Landi et al. 2002b)

• RESIK 3.3-6.1 A (Chifor et al. 2006)

• SMM - FCS 7-18 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=3,4,5,6,7 Fe XVII

n=3,4,5 Fe 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 withn=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

• 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 XIX Fe XX

FAC-DWTIPbase

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 XXIV innershell transitions

Fe II to Fe XXIV dielectronic satellite linesSi XII, S XVI, Ca XVIII dielectronic 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 XXV

Fe XXV

Fe XXIVsatellites

Fe XXIVsatellites

Fe XXIVsatellites

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: nq-1, nq, nq+1 ion fractions

CI, REC total ion. and rec. rates

Egi total excitation rate level i

Dig 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 LandiNaval Research Laboratory

Comparison with X-ray observations

We have compared the new CHIANTI 5.2 with observations of two moderate solar flares

Instrument SMM/FCS SMM/FCS

Date of observation August 25, 1980 July 2, 1985

Wavelength ranges 13.1-22.4 A 7.3-10.1 A

10.6-14.9 A

7.3-10.1 A

Spectral resolution 1-20 mA 1-5 mA

Source M 1.5 flare M 4.5 flare

Spectral scan Duration 17.5 minutes 27 minutes

Ions considered/available Fe XVII to Fe XXIII Fe XIX to Fe XXIV

Ni XIX, Ni XX

Ion N. lines Aug.25 Jul.2

Fe XVII 26 -Fe XVIII 40 -Fe XIX 43 3Fe XX 32 5Fe XXI 11 13Fe XXII 4 18Fe XXIII 3 9Fe XXIV - 7Ni XIX 5 -Ni XX 5 -

Total 169 55

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 4.2CHIANTI 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=3 Fe XVII to Fe XXIII

n=4 Fe XVII to Fe XIX

• Jul 2: n=4,5 Fe 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 14.6-16.4 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:

Ion Wvl.(A) Comment

Fe XVII 15.014 Long standing problemFe XIX,XX 13.091 Problem due to Fe XXFe XVII,XIX 10.655 Possibly mis-identified with line at 10.663 AFe XXI 9.587 Weak lineFe XXII 9.253Fe XXIII 8.304 Difficult benchmark due to paucity

of Fe XXIII lines

Results - IV

• Fe XVIII and Fe XIX had problems in the 14.6-16.4 A range (23 lines out of 224)

• Lines of each ion could be separated in a few groups:

• Fe XVIII: group A group B

• Fe XIX: group A group B group C

• The lines within groups showed a peculiar behaviour:

• Lines within each group agreed with each other

• Lines of different groups disagreed:– Fe XVIII: IA ~ 2 IB

– Fe XIX: IA~1.5 IB IA~3.6 IC

• 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:

Blending Unlikely Groups too well defined

Inaccurate wavefunctions Unlikely Included all configurations

Missing resonances Possible Need new calculations

Satellite lines Work 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 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» 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:

Process Importance

Cascades ModerateCollisional ionization ModerateRecombination CrucialResonances Crucial

• We have compared the FCS spectrum with predictions obtained with and without those processes

WITHOUT additional processes

WITH additional processes

15.01 A

15.01 A

•Still need some work on 15.01 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 forMost 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 14.6-16.4 A range