Recent advances in the CHIANTI database in the Xray range

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

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

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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

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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 (ngt2) in highly
• charged Fe and Ni ions
• Innershell transitions
• Dielectronic satellite lines
• Continuum radiation comes from
• Free-free radiation
• Free-bound radiation

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• 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

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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

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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 230 ions
• innershell transitions
• dielectronic satellite lines
• Continuum emissivities for free-free
  radiation
• free-bound radiation
• two-photon continuum
• Under the optically thin plasma assumption

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• 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_at_halcyon.nrl.navy.mil

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• 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

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State-of-the-art

• Literature data for the X-rays have several
  limitations
• Missing configurations (ngt3 in many Fe ions)
• Limited atomic models for n3 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

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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
• n3,4,5,6,7 Fe XVII
• n3,4,5 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

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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
• n3,4,5,6,7 Fe XVII
• n3,4,5 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)

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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 XXIII innershell transitions
• S XVI, Ca XVIII, Fe XXIV 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

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Fe XXV
Fe XXV
Fe XXV
Fe XXIV satellites
Fe XXIV satellites
Fe XXIV satellites
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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).

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• We make use of the Coronal Model Approximation
• Without Ionization/Recombination
• With Ionization/Recombination
• Where nq-1, nq, nq1 ion fractions
• CI, REC total ion. and rec. rates
• Egi total excitation rate level i
• Dig total de-excitation rate level i

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• 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 gt 13
• Fe XIX 12
• Fe XX 12
• Fe XXI 12
• Fe XXII 13
• Fe XXIII gt 13
• Fe XXIV any

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Fe XVII
Fe XVIII
Fe XX
Fe XIX
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Fe XXI
Fe XXII
Fe XXIV
Fe XXIII
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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

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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

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• 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.

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

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• We used CHIANTI 5.0 to check the importance of
  many additional processes in Fe XVII level
  population
• Process Importance
• Cascades Moderate
• Collisional ionization Moderate
• Recombination Crucial
• Resonances Crucial
• We have compared the FCS spectrum with CHIANTI
  5.0 predictions obtained with and without those
  processes

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CHIANTI 4.2
15.01 A
CHIANTI 5.0
15.01 A
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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