J/ApJS/213/11 UV spectrum of the quiet Sun above the limb (Warren+, 2014)
The absolute calibration of the EUV Imaging Spectrometer on Hinode.
Warren H.P., Ugarte-Urra I., Landi E.
<Astrophys. J. Suppl. Ser., 213, 11 (2014)>
=2014ApJS..213...11W 2014ApJS..213...11W
ADC_Keywords: Sun ; Spectra, ultraviolet
Keywords: Sun: corona
Abstract:
We investigate the absolute calibration of the EUV Imaging
Spectrometer (EIS) on Hinode by comparing EIS full-disk mosaics with
irradiance observations from the EUV Variability Experiment on the
Solar Dynamics Observatory. We also use extended observations of the
quiet corona above the limb combined with a simple differential
emission measure model to establish new effective area curves that
incorporate information from the most recent atomic physics
calculations. We find that changes to the EIS instrument sensitivity
are a complex function of both time and wavelength. We find that the
sensitivity is decaying exponentially with time and that the decay
constants vary with wavelength. The EIS short wavelength channel shows
significantly longer decay times than the long wavelength channel.
Description:
First, we compare full-disk mosaics constructed by scanning the EIS
slot over the Sun with irradiance observations made by the EUV
Variability Experiment (EVE; Woods et al. 2012SoPh..275..115W 2012SoPh..275..115W) on the
Solar Dynamics Observatory (SDO) mission. These comparisons provide a
means of establishing the absolute calibration for EIS. Second, we
combine extended EIS observations from above the limb in the quiet Sun
with a simple temperature model to simultaneously determine the
differential emission measure (DEM) distribution and the
time-dependent changes to the effective areas that best fit all of the
available spectral lines.
In Figure 2 we show the average spectrum from an observation of seven
consecutive runs of ELFULLCCDWSUMER. The observations began on
2007 November 4 19:12 and ended on the same date at 23:51 UT. The EIS
field of view was centered at (990", -50") about 22" above the limb of
the Sun. The central 129 pixels along the slit have been averaged over
38 exposures (11 exposures were corrupted in transmission to the
ground) for a total of 4902 intensity measurements at each wavelength.
Since each exposure is 300s, the spectrum represents 1470600 pixels of
effective exposure time and allows weak lines at the ends of the
detector to be measured.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 72 16384 *Spectrum of the quiet Sun above the limb
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Note on fig2.dat: Spectrum of the quiet Sun above the limb constructed by
averaging 38x300s exposures and 129 pixels along the 2" slit for an effective
exposure time of 1470600s. The scale in the Y direction has been cutoff to
emphasize the weak lines. The peak count rates are approximately 50/s.
See figure 2.
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See also:
J/ApJ/759/141 : Emission measures in solar active regions (Warren+, 2012)
J/A+A/432/1063 : Analysis of inner solar corona in EUV (Lanzafame+, 2005)
J/ApJ/543/1016 : Solar active region EUV spectrum from SERTS-97 (Brosius+ 2000)
J/A+AS/125/149 : CHIANTI: An Atomic Database For Emission Lines I. (Dere+ 1997)
J/ApJS/91/461 : EUV spectrum of solar active region (Thomas+, 1994)
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "YYYY/MM/DD" Date Date of the observation (UT): 2007-11-04,
2010-10-16, 2012-08-09 or 2013-07-20
12- 18 F7.3 0.1nm lambda [166/292] Wavelength λ in Angstroms
20- 27 E8.3 ct/s/pix Iraw Uncalibrated intensity (1)
29- 36 E8.3 ct/s/pix e_Iraw Uncertainty on Idn
38- 45 E8.3 cW/m2/sr/nm Ipre Pre-flight calibrated intensity (2)
47- 54 E8.3 cW/m2/sr/nm e_Ipre Uncertainty on PreCint (2)
56- 63 E8.3 cW/m2/sr/nm Ical Corrected calibrated intensity (2)
65- 72 E8.3 cW/m2/sr/nm e_Ical Uncertainty on CCInt (2)
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Note (1): In units of data number (DN) per second per spectral pixel.
Note (2): In units of erg/cm2/s/sr/Angstrom.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 02-Sep-2014