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SBUV/2 Solar UV Flux/Magnesium-II Index


Availability: Data Accessible Elsewhere

Time span: 1989-02-01 to 1992-01-31


The solar measurements from the Solar Backscatter Ultraviolet (SBUV) experiment on Nimbus-7 and SBUV/2 on NOAA-9 and NOAA-11 is the fourth data set on the third TOMS CD-ROM volume. The SOLAR data was collected by the SBUV and SBUV/2 for the period November 1, 1978 through January 31, 1992. The data set consists of composite Magnesium II (Mg II) index, scale factor data, and reference solar spectrum data. The composite Mg II index is a daily measurement of the solar ultraviolet variability using the Mg II absorption feature at 280 nm. The Mg II index can be used in conjunction with the composite scale factors to estimate solar irradiance variations at any wavelength in the 170-400 nm wavelength range. The Mg II index is a dimensionless quantity measuring mid-ultraviolet solar activity. It is a ratio of irradiances, where the numerator consists of the average of three consecutive wavelength samples at the core of the unresolved Mg II h & k doublet at 280 nm, and the denominator is the average of two pairs of consecutive wavelengths equally spaced approximately 3 nm from the core wavelength. The Mg II index was constructed from SBUV data on Nimbus-7 and SBUV/2 data on NOAA-9 and NOAA-11. The Nimbus-7 Mg II index data is from November 1978 to March 1987. The NOAA-9 Mg II index data is from March 1985 to September 1990. The NOAA-11 Mg II index data is from February 1990 to January 1992. The composite Mg II index data are referenced to the NOAA-9 SBUV/2 absolute reference scale. The data set consists of the composite daily Mg II index data. A 5-day binomial-weighted average has been applied to the data set. The Mg II data are in ASCII format and the data records contain the year, day-of-year, Julian day (beginning 1 January 1978), and the Mg II index value. The composite scale factors data set contains scaling factors which can be used to estimate the solar irradiance variability at other UV wavelengths. The scale factor data are a combination of the best results for Nimbus-7, NOAA-9 and NOAA-11. The composite scale factor data are in ASCII and consists of the wavelength (170-400 nm) at 1 nm spacing, the composite scale factor, and the weighted average of standard deviation values. The reference solar spectrum is the absolute solar spectral irradiance values in the mid-UV wavelength region for Nimbus-7. The spectrum is an average of five separate spectra taken from November 7-12, 1978, and interpolated to a 0.2 nm grid using a cubic spline. The solar irradiance data are in ASCII and consists of the wavelength (170-400 nm) at 0.2 nm spacing, and the irradiance in W/cm**2/cm. See Cebula, R.P.,, "Intercomparisons of the Solar Irradiance Measurements from the Nimbus-7 SBUV, the NOAA-9 and NOAA-11 SBUV/2, and the STS-34 SSBUV Instruments: A Preliminary Study", J.Atmo. Terr. Phys. 53, 993-997, 1991; Heath, D.F. and B. M. Schlesinger, "The Mg 280-nm Doublet as a Monitor of Changes in the Solar Ultraviolet Irradiance", J. Geophys. Res., 91, 8672-8682, 1986. See NSSDC ID 78-098A-09e and 84-123A-07A.

This data set has been transferred to the Goddard DAAC in April 1994.

Alternate Names

  • SBUV/2 MG-II Index/Solar UV Flux


  • Earth Science: Atmospheric Chemistry
  • Solar Physics: Ultraviolet


  • 88-089A-05A

Additional Information



Questions and comments about this data collection can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Dr. Richard D. McPetersData ProviderNASA Goddard Space Flight
Mr. David E. LarkoGeneral ContactHughes STX
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