Solar Ultraviolet Spectral Irradiance

Table Of Contents:

1.) SOLAR2000 Model (K. Tobiska) Feb 1947-present

2.) NOAA MgII Core-to-wing ratio data 1978-present (R. Viereck)

3.) SORCE (Solar Radiation and Climate Experiment) satellite data 2003-present (G. Rottman)

4.) Older archival databases:

4a.) Dr. John Arvesen's Solar Spectral Irradiance data at the top of the atmosphere in the 300-2500 nm wavelength range (UV to visible), from NASA research aircraft -- 11 flights

4b.) Atmospheric Explorer E (AE-E) extreme ultraviolet (EUV) spectrometer flux data by Hinteregger

4c.) Mid-UV Balloon Measurements -- 1978 and 1983 flight data from AFGL (G. Anderson and L. Hall)

4d.) NIMBUS 7 Solar UV Core-to-Wing Ratio for the Mg II H and K lines 1978-1988 (R. Donnelly)

4e.) NOAA9 SBUV2 Solar Ultraviolet Data 1986-1988 (R. Donnelly)

4f.) Pioneer-Venus EUV data Jan. 3, 1979-Jan. 29, 1992 (D. Pesnell and W. Hoegy)

4g.) Oxygen Schumann-Runge band temperature dependent cross sections in the UV (G. Anderson)

4h.) EUV91 SERF2 -- Solar Extreme UV Flux model (K. Tobiska)

4i.) SME Solar Mesosphere Explorer Satellite Lyman-alpha fluxes Jan 1, 1982-Mar 31, 1989 (Univ of Colorado)

4j.) SOLSTICE Solar-Stellar Irradiance Comparison Experiment UARS solar ultraviolet data October 3, 1991-Sep 30, 1994 (G. Rottman)

4k.) SUSIM Solar Ultraviolet Spectral Irradiance Monitor on UARS Mg II Index Oct. 15, 1991-June 24, 1997 (G. Brueckner, D. Prinz, L. Floyd)

Solar Ultraviolet (All ftp)

The ultraviolet (UV) part of the electromagnetic spectrum ranges between 5 and 400 nanometers (nm). As the SORCE (Solar Radiation and Climate Experiment satellite) mission states, far UV irradiance from the Sun varies by as much as 10 percent during the Sun's 27-day rotation, while the bright 121.6 nm hydrogen Lyman-alpha emission may vary by as much as a factor of 2 during an 11-year solar cycle, dramatically affecting the energy input into the Earth's atmosphere. Water vapor and ozone are especially sensitive to changes in the solar UV radiation. Different wavelengths of solar radiation are absorbed at different altitudes in the Earth's atmosphere, affecting different physical processes. As Dr. Jack Eddy notes, we utterly depend on solar radiation. Long term monitoring of its variations over all wavelengths is critical to our understanding of the impacts on our environment.

1. SOLAR2000 model descriptive text -- web site
  • SOLAR2000 is an empirical solar irradiance specification tool for accurately characterizing solar irradiance variability across the solar spectrum. SOLAR2000 is designed to be a fundamental energy input into planetary atmosphere models, a comparative model with numerical first-principles solar models, and a tool to model or predict the solar radiation component of the space environment. SOLAR2000 includes a new EUV proxy, E10.7, which has the same units as the commonly used F10.7 cm solar radio flux. E10.7 can be used in existing models where F10.7 is traditionally used, but it offers significant improvement as an index of the energy input to the thermosphere and ionosphere.
    • An extracted data base from SOLAR2000 version v1.23a of the E10.7 proxy for the time period of Feb 14, 1947 through May 31, 2002 is a particularly useful data set for climate studies and for those who want a long time series of Lyman-alpha and/or E10.7. The five solar cycle file of data contains one record (or line) for each day with date/time, F10.7, 81-day F10.7, Lyman-alpha, 81-day Lyman-alpha, E10.7, 81-day E10.7, and the solar constant S(t) (variable in EUV wavelengths only in this version).
      • Plots of five solar cycles of the daily F10.7 cm solar radio data adjusted to 1 AU, the E10.7 EUV proxy index, and a Lyman-alpha index (from Mg II index) are available.

2. NOAA Mg II Core-to_wing ratio data
  • 1978-present are provided by Dr. R. Viereck, NOAA Space Environment Center.
  • The Mg II core-to-wing ratio is derived from the ratio of the h and k lines of the solar Mg II feature at 280 nm to the background or wings at approximately 278 nm and 282 nm. The h and k lines are variable chromospheric emissions while the background emissions are more stable. The result is a robust measure of chromospheric activity. The ratio is a good measure of solar UV and EUV emissions.

3. Solar Spectral Irradiance data from the SORCE (Solar Radiation and Climate Experiment) satellite:
  • SORCE (Solar Radiation and Climate Experiment) was launched on Jan 25, 2003, to provide precise measurements of solar radiation. It is operated by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado (CU) in Boulder, Colorado, USA. SORCE provides measurements of the solar spectral irradiance from 1nm to 2000nm, accounting for 95% of the spectral contribution to the Total Solar Irradiance (TSI). SORCE carries four instruments including the Total Irradiance Monitor (TIM), Solar Stellar Irradiance Comparison Experiment (SOLSTICE), Spectral Irradiance Monitor (SIM), and the XUV Photometer System (XPS).
  • For data information, please visit the SORCE (Solar Radiation and Climate Experiment) website. The primary repository and access node for SORCE data is the Goddard Earth Sciences (GES) Distributed Active Archive Center (DAAC) in Greenbelt, Maryland, USA. Please visit the NASA DAAC or the SORCE webpage to access these data.


4. Older archival databases:
  • 4a. Dr. John C. Arvesen's solar spectral irradiance at the top of the atmosphere -- UV to visible (200-2495 nm)
    • NASA research aircraft database (txt) including descriptive text
      • Results are presented of an experiment to determine extraterrestrial solar spectral irradiance at the Earth's mean solar distance within the 300-2500 nm wavelength region. Spectroradiometric measurements were performed during eleven research flights on board a NASA CV-990 aircraft at altitudes between 11.6 km and 12.5 km. Precision of the measurements was better than +/- 1 percent. Absolute accuracy of the resultant extraterrestrial solar spectral irradiance is about +/-3 percent over most of the measurement range. A listing of results is presented at intervals varying from 0.1 nm throughout most of the uv-visible Fraunhofer region to 5 nm in the continuum region of the infrared. Additionally, a listing of solar spectral irradiance, smoothed over the detailed Fraunhofer structure, is presented for engineering use.
  • 4b. Atmospheric Explorer E (AE-E) extreme ultraviolet (EUV) spectrometer flux data by H.E. Hinteregger.

    A status of SERF1 (WORD document) is available. Several problems with the data are discussed. Solar spectrum experts strongly encourage everyone to use the latest solar EUV spectrum model SOLAR2000.

    • EUV flux data sc21obsc.dat from the Extreme UltraViolet Spectrometer (EUVS) on Atmosphere Explorer E (AE-E) (descriptive text) cover 15 wavelength groups for the time period from the 182nd day of 1977 to the 160th day of 1981. A program was written by Dean Pesnell to read the EUV data file.
    • The data are normalized to the reference spectrum SC21REFW.DAT. The EUV reference spectra and related EUV model parameters are based on the measurements and work of H.E. Hinteregger and his colleagues. The model and reference spectra (R74113, F74113, F76REF, SC21REFW) are described by Hinteregger et al. (GRL 8, 1147, 1981). The spectra and model are based on rocket measurements and simultaneously obtained EUV fluxes by the AE-C and AE-E spectrometer.
    • The EUVS instrument is described in an article by Hinteregger in Radio Science, Vol. 8, No. 4, 349-360, 1973. Other references are available. Hans Hinteregger's Explanation (8 Megabyte file) of the EUV reference spectrum and notes of EUV flux observations are also available.
  • 4c. Mid-UV Balloon Measurements -- 1978 and 1983 flight data from AFGL (G. Anderson and L. Hall) -- descriptive text
    • The solar spectra files contain the wavelength in Angstroms and the solar irradiance in photons cm-2 s-1 A-1. The instrument had two detectors in the focal plane, one giving the spectrum in 0.1 A resolution and the other in 1.0 A resolution, both with a wavelength step increment of .02 A.
      • File d78tnth83 data are 0.1A resolution, block averaged over 5 samples in the raw data. For wavelengths 2000 to 2077.4A, the spectrum form the 1983 measurement was used. For 2077.5 to 3100 A, the 1978 flight data were used.
      • File afgl83 data are from the 1983 flight, in 1.0 A resolution, in steps of 0.5A.
      • The measurements were made from a balloon near 40 km and extrapolated to zero optical depth by correcting for ozone, O2 Herzberg continuum absorption, and Rayleigh scattering. No correction is made for Schumann-Runge absorption, so there is some slight signature from the 0-0 and 1-0 bands of that system near 2000 A and 2025 A.
  • 4d. NIMBUS 7 Solar UV Core-to-Wing Ratio for the Mg II H and K lines, 1978-1988 (R. Donnelly)
    • The descriptive text describes Heath and Schlesinger's work on the Solar Backscatter Ultraviolet (SBUV) experiment on the NIMBUS7 satellite. They showed that the core-to-wing ratio of Mg II h and k lines was a good measure of the temporal variaitons of the solar UV flux, including long-term variations, because the ratio is relatively insensitive to drifts in instrument sensitivity. These NIMBUS data are not normalized to solar cycle minimum.
  • 4e. NOAA9 SBUV2 Solar UV data 1986-1988 (R. Donnelly)
    • Mg II core-to-wing ratio developed by Heath and Schlesinger for solar UV measurements on SBUV NIMBUS7 experiment are extended to the SBUV2 NOAA9 satellite data. A modified ratio is used to reduce noise. Values are converted to equivalent Nimbus7 values using a linear regression relation. See descriptive text.
  • 4f. Pioneer-Venus EUV data Jan. 3, 1979-Jan 29, 1992 (D. Pesnell and W. Hoegy)
    • The Ipe Solar EUV Flux Index comes from a rhenium-coated Langmuir probe on Pioneer Venus Orbiter. The descriptive text explains how the flux is monitored. There are 4096 data vlues, with gaps up to 37 days in length. The solar rotation period is roughly 29 days when viewed from Venus, not 27 days as seen from Earth.
    • Pioneer-Venus Orbiter Langmuir Probe database -- date is YYYYMMDD and the Ipe current is in nanoamps.

  • 4g. Oxygen Schumann-Runge band temperature dependent cross sections in the UV (G.P. Anderson)
    • Descriptive text -- The three files contain polynomial coefficients for generating oxygen Schumann-Runge cross sections. The coefficients span the spectral range 49,000 to 57,000 cm-1, recorded at 0.5 cm-1 intervals. Calculated cross sections will represent Schumann-Runge band and continuum corss sections only. The Herzberg continuum cross section, if desired, must be added separately. See the appendix in the readme file for a typical Fortran program for an isothermal path.
    • The readme file suggests using file 130-190.cf4 for temperatures between the range 130K to 190K, use file 190-280.cf4 for temperatures between 190K to 280K, and use file 280-500.cf4 for temperatures between 280K to 500K. Please note that the polynomial-generated cross sections will be significantly in error if calculated outside of these bounds.
    • Each of the three files contains six columns -- Column 1 = Wavenumber (cm-1); Column 2 = Coefficient A; Column 3 = Coefficient B; Column 4 = Coefficient C; Column 5 = Maximum percent error in fit over the relevant temperature rante; and Column 6 = Temperature at which maximum error occurs.
    • For additional information, please refer to Minschwaner, K., G.P. Anderson, L.A. Hall, and K. Yoshino, Polynomial Coefficients for Calculating O2 Schumann-Runge Cross Sections at 0.5 cm-1 Resolution, J. Geophys. Res., Vol 97, pp. 10.103-10.108, 1992.
  • 4h. EUV91 SERF2 -- Solar Extreme UV Flux model (K. Tobiska)
    • The status of SERF1 (WORD document) is available. The Hinteregger SERF1 data files are available in 3b. Atmospheric Explorer E (AE-E). Several problems are discussed. Solar spectrum experts strongly encourage everyone to use the latest solar EUV spectrum model SOLAR2000. An intermediate model SERF2 is discussed in REVISED SOLAR EXTREME ULTRAVIOLET FLUX MODEL by W. Kent Tobiska, J. Atmos. Terr. Phys.
      • SERF2 documentation and Fortran code is available. This Fortran program creates the solar EUV irradiance for 18-1050 A based multiple linear regression model for solar EUV flux.
      • The files for the solar EUV91 model include: 1) euv91.doc documentation, 2) jatp.txt (text file which is the same as the JATP journal article), 3) coeff.txt (table of coefficients for the model), 4) euv91.for (FORTRAN 77 code), 5) euv91_a.pro and euv91_b.pro (IDL code), 6) index_2.dat (data file: date, Lyman-alpha, He I 10,830, F10.7, F10.7 81-day mean values for YYDOY 47001-68172). 7) index_1.dat (data file: date, Lyman-alpha, He I 10,830, F10.7, F10.7 81-day mean values for YYDOY 68173-88366). 8) index_3.dat (data file: date, Lyman-alpha, He I 10,830, F10.7, F10.7 81-day mean values for YYDOY 89001-90365).
  • 4i. SME Solar Mesosphere Explorer Satellite Daily Solar Lyman-alpha emission fluxes Jan 1, 1982-Mar 31, 1989 (Univ of Colorado)
    • Lyman-alpha is a strong emission line of hydrogen in the sun's radiation spectrum at the ultraviolet wavelength of 121.5 nanometers. Variations in its intensity track the erratic 11-year rise and fall of solar activity. This database contains fluxes measured with the University of Colorado's Solar Mesosphere Explorer Satellite (SME). Observations cover the period 1 Jan 1982 through 31 Mar 1989 at a resolution of 1 nanometer. Each daily value is an average of multiple measurements expressed in units of 10 to the 11th photons/square centimeter/second/nanometer. In the file LYMAN_A.PLT, the quality flag shows what fraction (0 to 1) of the tabulated value was derived from actual measurements rather than from time-averaged running means.
    • Files:
      • contents -- definition of measurement and of files
      • lyman_a.yy -- table of daily values for year indicated in units of 10 to the 11th photons/square centimeter/second/nanometer
    • lyman_a.plt -- all values in column form suitable for plotting.
  • 4j. SOLSTICE Solar-Stellar Irradiance Comparison Experiment UARS solar ultraviolet data -- descriptive text October 3, 1991-Sep 30, 1994 (G. Rottman)
    • The Upper Atmosphere Research Satellite (UARS) data set consists of daily near global (N80 - S80) measurements of atmospheric trace gases and wind profiles, as well as measurements of solar UV spectra and charged particles injected into the Earth's atmosphere. The Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) instrument measures the solar ultraviolet spectra in the 119 nm - 420 nm range. The data are archived at the Goddard Distributed Active Archive Center (DAAC). Version 7 data (Oct 1994) presented here include Mg II 280.0 nm and Ca II 393.3 nm core-to-wing ratios, Hydrogen I Lyman alpha 121.6 nm intensities, and 200-205 nm summed intensities. Only selected years (1991-1994) of data are available here.
  • 4k. SUSIM Solar Ultraviolet Spectral Irradiance Monitor on Mg II Index Oct. 15, 1991-June 24, 1997 (G. Brueckner, D. Prinz, L. Floyd) on UARS -- descriptive text and references -- See also the NASA DAAC site for SUSIM data.
    • The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) on the Upper Atmospheric Research Satellite (UARS) has been measuring the solar spectral irradiance from 115 nm to 410 nm since 12-October-1991 (UARS mission day 31). Once per day, spacecraft power permitting, SUSIM obtains one complete solar UV spectrum at each of two spectral resolutions (5 nm and 1.1 nm (FWHM)) and five intervals of a few nanometers each, over strong solar emission or absorption lines, at 0.15 nm (FWHM) resolution. Once per week SUSIM also obtains one complete UV spectrum at 0.15 nm (FWHM) resolution, and observes four sequential sunrises (UARS flying forward) or sunsets (UARS flying backward) at a wavelength absorbed by molecular oxygen or ozone.
    • A Mg II index is computed from the daily mid-resolution spectrum in the vicinity of 280 nm. At this spectral resolution (1.1 nm FWHM, sampled every ~0.24 nm) the Mg II absorption doublet and the chromospheric emission line in the core of each absorption line, are blended so that the feature appears to be a single absorption "line". The SUSIM Mg II index is a ratio of a measure of the "core" of the feature to a similar measure of the wings of the feature. There have been two definitions for the index, as discussed on the SUSIM Web page.
    • Daily MgII Index in annual files -- format

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