J/A+A/626/A123 Electron impact ionisation data (Dufresne+, 2019)
Modelling ion populations in astrophysical plasmas:
carbon in the solar transition region.
Dufresne R.P., Del Zanna G.
<Astron. Astrophys. 626, A123 (2019)>
=2019A&A...626A.123D 2019A&A...626A.123D (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: Sun: transition region - atomic data - atomic processes
Abstract:
The aim of this work is to improve the modelling of ion populations in
higher density, lower temperature astrophysical plasmas, of the type
commonly found in lower solar and stellar atmospheres. Ion population
models for these regions frequently employ the coronal approximation,
which assumes conditions more suitable to the upper solar atmosphere,
where high temperatures and lower densities prevail. The assumed
conditions include all ions being in the ground state and steady-state
equilibrium, where there is sufficient time for ionisation and
recombination to take place. Using the coronal approximation for
modelling the solar transition region gives theoretical lines
intensities for the Li-like and Na-like isoelectronic sequences which
are often factors of two to five times lower than observed. The works
of Burgess & Summers (1969ApJ...157.1007B 1969ApJ...157.1007B) and Nussbaumer & Storey
(1975A&A....44..321N 1975A&A....44..321N) show the important part ions in excited levels
play when included in the modelling. As density increases metastable
levels become populated and ionisation rates increase, whereas
dielectronic recombination through highly excited levels is
suppressed. Photo-ionisation is also shown by Nussbaumer & Storey to
have an effect on the charge-state distribution of carbon in these
regions. Their models, however, use approximations for the atomic
rates to determine the ion balance. Presented here is the first stage
in rates to determine the ion balance. Presented here is the first
stage in updating these earlier models of carbon by using rates from
up-to-date atomic calculations and more recent photo-ionising
radiances. Where atomic rates were not readily available, in the case
of electron impact direct ionisation and excitation-auto-ionisation,
new calculations were made using the Flexible Atomic Code and
Autostructure, and compared to theoretical and experimental studies.
The effects each atomic process has on the ion populations as density
changes is illustrated, and final results from the modelling are
compared to the earlier works. Lastly, the new results for ion
populations were used to predict line intensities for the solar
transition region in the quiet Sun. In comparison to coronal
approximation modelling the new results show significantly improved
agreement with observations.
Description:
The file levels.dat gives indices for energy levels of ions for which
data has been given. The file temps.dat gives the temperatures at
which the rate coefficients have been calculated for each ion. The
file di_rates.dat gives the rate coefficients for direct ionisation
(DI) by electron impact and the file ea_rates.dat gives the rate
coefficients for excitation--auto-ionisation (EA) by electron impact.
Details of methods for calculations given in the paper and at
https://arxiv.org/abs/1901.08992.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
levels.dat 56 14 Energy level index and their configurations
temps.dat 153 4 Temperatures for rate coefficients
di_rates.dat 175 29 DI Rate coefficients
ea_rates.dat 175 35 EA Rate coefficients
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Byte-by-byte Description of file: levels.dat
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Bytes Format Units Label Explanations
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5 I1 --- Z Atomic number of element
10 I1 --- N Number of electrons in ion
15 I1 --- Level Energy level index
18- 28 A11 --- Config Electron configuration of level
39 I1 --- S Spin angular momentum of level
42 I1 --- L Orbital angular momentum of level
45 I1 --- 2J Total angular momentum of level x2
48- 56 E9.4 eV dE Level energy relative to ground level of ion
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Byte-by-byte Description of file: temps.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
5 I1 --- Z Atomic number of element
10 I1 --- N Number of electrons in ion before impact
13- 21 E9.4 K Temp1 Temperature 1
24- 32 E9.4 K Temp2 Temperature 2
35- 43 E9.4 K Temp3 Temperature 3
46- 54 E9.4 K Temp4 Temperature 4
57- 65 E9.4 K Temp5 Temperature 5
68- 76 E9.4 K Temp6 Temperature 6
79- 87 E9.4 K Temp7 Temperature 7
90- 98 E9.4 K Temp8 Temperature 8
101-109 E9.4 K Temp9 Temperature 9
112-120 E9.4 K Temp10 Temperature 10
123-131 E9.4 K Temp11 Temperature 11
134-142 E9.4 K Temp12 Temperature 12
145-153 E9.4 K Temp13 Temperature 13
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Byte-by-byte Description of file: di_rates.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Z Atomic number of element
6- 10 I5 --- N Number of electrons in ion before impact
11- 15 I5 --- ilevel Initial level of ion before impact
16- 20 I5 --- flevel Final level after impact of ionised ion
24- 32 E9.4 eV IP Threshold energy for process
34- 43 E10.4 cm+3/s Rate1 Rate coefficient at Temp1(Z,N)
46- 54 E9.4 cm+3/s Rate2 Rate coefficient at Temp2(Z,N)
56- 65 E10.4 cm+3/s Rate3 Rate coefficient at Temp3(Z,N)
68- 76 E9.4 cm+3/s Rate4 Rate coefficient at Temp4(Z,N)
79- 87 E9.4 cm+3/s Rate5 Rate coefficient at Temp5(Z,N)
90- 98 E9.4 cm+3/s Rate6 Rate coefficient at Temp6(Z,N)
101-109 E9.4 cm+3/s Rate7 Rate coefficient at Temp7(Z,N)
112-120 E9.4 cm+3/s Rate8 Rate coefficient at Temp8(Z,N)
123-131 E9.4 cm+3/s Rate9 Rate coefficient at Temp9(Z,N)
134-142 E9.4 cm+3/s Rate10 Rate coefficient at Temp10(Z,N)
145-153 E9.4 cm+3/s Rate11 Rate coefficient at Temp11(Z,N)
156-164 E9.4 cm+3/s Rate12 Rate coefficient at Temp12(Z,N)
167-175 E9.4 cm+3/s Rate13 Rate coefficient at Temp13(Z,N)
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Byte-by-byte Description of file: ea_rates.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Z Atomic number of element
6- 10 I5 --- N Number of electrons in ion
11- 15 I5 --- ilevel Initial level of ion before impact
16- 20 I5 --- flevel Final level after impact of ionised ion
24- 32 E9.4 eV IP Threshold energy for process
34- 43 E10.4 cm+3/s Rate1 Rate coefficient at Temp1(Z,N)
45- 54 E10.4 cm+3/s Rate2 Rate coefficient at Temp2(Z,N)
56- 65 E10.4 cm+3/s Rate3 Rate coefficient at Temp3(Z,N)
68- 76 E9.4 cm+3/s Rate4 Rate coefficient at Temp4(Z,N)
79- 87 E9.4 cm+3/s Rate5 Rate coefficient at Temp5(Z,N)
90- 98 E9.4 cm+3/s Rate6 Rate coefficient at Temp6(Z,N)
101-109 E9.4 cm+3/s Rate7 Rate coefficient at Temp7(Z,N)
112-120 E9.4 cm+3/s Rate8 Rate coefficient at Temp8(Z,N)
123-131 E9.4 cm+3/s Rate9 Rate coefficient at Temp9(Z,N)
134-142 E9.4 cm+3/s Rate10 Rate coefficient at Temp10(Z,N)
145-153 E9.4 cm+3/s Rate11 Rate coefficient at Temp11(Z,N)
156-164 E9.4 cm+3/s Rate12 Rate coefficient at Temp12(Z,N)
167-175 E9.4 cm+3/s Rate13 Rate coefficient at Temp13(Z,N)
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Acknowledgements:
Roger Dufresne, rpd21(at)cam.ac.uk
Giulio Del Zanna, gd232(at)cam.ac.uk
(End) Patricia Vannier [CDS] 06-Jun-2019