J/ApJ/789/117 Solar spectral irradiance (Marchenko+, 2014)
Solar spectral irradiance changes during cycle 24.
Marchenko S.V., Deland M.T.
<Astrophys. J., 789, 117 (2014)>
=2014ApJ...789..117M 2014ApJ...789..117M (SIMBAD/NED BibCode)
ADC_Keywords: Sun ; Spectra, ultraviolet
Keywords: Sun: activity - Sun: atmosphere - Sun: rotation - Sun: UV radiation
Abstract:
We use solar spectra obtained by the Ozone Monitoring Instrument (OMI)
on board the Aura satellite to detect and follow long-term (years) and
short-term (weeks) changes in the solar spectral irradiance (SSI) in
the 265-500 nm spectral range. During solar Cycle 24, in the
relatively line-free regions the SSI changed by ∼0.6%±0.2% around
265 nm. These changes gradually diminish to 0.15%±0.20% at 500 nm.
All strong spectral lines and blends, with the notable exception of
the upper Balmer lines, vary in unison with the solar "continuum."
Besides the lines with strong chromospheric components, the most
involved species include Fe I blends and all prominent CH, NH, and CN
spectral bands. Following the general trend seen in the solar
"continuum," the variability of spectral lines also decreases toward
longer wavelengths. The long-term solar cycle SSI changes are closely,
to within the quoted 0.1%-0.2% uncertainties, matched by the
appropriately adjusted short-term SSI variations derived from the 27
day rotational modulation cycles. This further strengthens and
broadens the prevailing notion about the general scalability of the UV
SSI variability to the emissivity changes in the Mg II 280 nm doublet
on timescales from weeks to years. We also detect subtle deviations
from this general rule: the prominent spectral lines and blends at
λ ≳ 350 nm show slightly more pronounced 27 day SSI changes
when compared to the long-term (years) trends. We merge the solar data
from Cycle 21 with the current Cycle 24 OMI and GOME-2 observations
and provide normalized SSI variations for the 170-795 nm spectral
region.
Description:
Combining the contemporaneous Ozone Monitoring Instrument (OMI) and
GOME-2 observations with the records from previous solar cycles, we
construct the normalized (to the Mg II doublet at 280 nm) solar
variability spectrum in the 170-795 nm spectral range, which could
be used in combination with a reference spectrum (e.g., Thuillier et
al. 2004, Solar Variability and its Effects on Climate (Geophysical
Monograph 141), ed. J. M. Pup et al. (Washington, DC: AGU Geophysical
Monograph Series), 171) to reproduce a dynamical solar spectrum at any
epoch.The remote-sensing OMI (part of the Aura instrumental suite;
Levelt et al., 2006ITGRS..44.1093L 2006ITGRS..44.1093L) has collected information about
trace gases in the Earth's atmosphere since 2004 July. OMI comprises
three different spectral channels, UV1 (264-311 nm spectral domain,
resolution δλ = 0.63 nm), UV2 (307-383 nm,
δλ = 0.42 nm), and VIS (349-504 nm, δλ =
0.63 nm), each acquiring data through partially shared optical
pathways (Dobber et al., 2006ITGRS..44.1209D 2006ITGRS..44.1209D). The UV1 and UV2 light
falls on the same CCD detector while VIS spectra are recorded by a
different CCD.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 18 3145 The normalized max-min difference spectra
derived from the 27-day rotational modulation
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See also:
J/A+A/587/A65 : Visible and near-infrared solar spectra (Reiners+, 2016)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 nm Wave Wavelength
7- 12 F6.3 % Diff Normalized max-min spectral difference (1)
14- 18 F5.3 % e_Diff The 1σ error in Diff
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Note (1): Derived from the 27-day rotational modulation.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 09-Mar-2017