J/A+A/668/A9 Center-to-limb distribution of SiI line width (Hong+, 2022)
Statistical analysis of the Si I 6560.58 Å line observed by CHASE.
Hong J., Qiu Y., Hao Q., Xu Z., Li C., Ding M., Fang C.
<Astron. Astrophys. 668, A9 (2022)>
=2022A&A...668A...9H 2022A&A...668A...9H (SIMBAD/NED BibCode)
ADC_Keywords: Equivalent widths ; Sun
Keywords: line: formation - line: profiles - Sun: photosphere - turbulence
Abstract:
The SiI 6560.58Å line in the Hα blue wing is blended with a
telluric absorption line from water vapor in ground-based
observations. Recent observations with the space-based telescope CHASE
provide a new window to study this line. We aim to study the SiI line
statistically and to explore possible diagnostics. We select three
scannings in the CHASE observations, and measure the equivalent width
(EW) and the full width at half maximum (FWHM) for each pixel on the
solar disk. We then calculate the theoretical EW and FWHM from the
VALC model. An active region is also studied in particular for
difference in the quiet Sun and the sunspots. The SiI line is formed
at the bottom of the photosphere. The EW of this line increases from
the disk center to mu=0.2, and then decreases toward the solar limb,
while the FWHM shows a monotonically increasing trend. Theoretically
predicted EW agrees well with observations, while the predicted FWHM
is far smaller due to the absence of unresolved turbulence in models.
The macroturbulent velocity is estimated to be 2.80km/s at the disk
center, and increases to 3.52km/s at mu=0.2. We do not find any
response to flare heating in current observations. Doppler shifts and
line widths of the SiI 6560.58Å and FeI 6569.21Å lines can be
used to study the mass flows and turbulence of the different
photospheric layers. The SiI line has good potentials to diagnose the
dynamics and energy transport in the photosphere.
Description:
Center-to-limb distribution of the EW and the FWHM of the SiI line
from model calculations and observed mean values. An instrumental FWHM
of 72.6mÅ is included.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 74 9 Center-to-limb distribution of Si i line width
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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2- 4 F3.1 --- mu Cosine of heliocentric angle
6- 10 F5.2 0.1pm EW-VALC Calculated equivalent width in VALC model
12- 16 F5.2 0.1pm EW-OBS1m Mean value of equivalent width in OBS1
19- 22 F4.2 0.1pm s_EW-OBS1m Standard deviation of EW in OBS1
24- 28 F5.2 0.1pm EW-OBS2m Mean value of equivalent width in OBS2
31- 34 F4.2 0.1pm s_EW-OBS2m Standard deviation of EW in OBS2
36- 40 F5.2 0.1pm EW-OBS3m Mean value of equivalent width in OBS3
43- 46 F4.2 0.1pm s_EW-OBS3m Standard deviation of EW in OBS3
48- 50 I3 0.1pm FWHM-VALC Calculated FWHM in VALC model
52- 54 I3 0.1pm FWHM-OBS1m Mean value of FWHM in OBS1
57- 58 I2 0.1pm s_FWHM-OBS1m Standard deviation of FWHM in OBS1
60- 62 I3 0.1pm FWHM-OBS2m Mean value of FWHM in OBS2
65- 66 I2 0.1pm s_FWHM-OBS2m Standard deviation of FWHM in OBS2
68- 70 I3 0.1pm FWHM-OBS3m Mean value of FWHM in OBS3
73- 74 I2 0.1pm s_FWHM-OBS3m Standard deviation of FWHM in OBS3
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Acknowledgements:
Jie Hong, jiehong(at)nju.edu.cn
(End) Jie Hong [NJU, China], Patricia Vannier [CDS] 28-Sep-2022