Comparisons of the Mg II index products from the NOAA-9 and NOAA-11 SBUV/2 Instruments

The Mg II Index is a proxy indicator of solar UV activity which is produced from measurements of the chromospheric Mg II absorption line at 280 nm. Mg II index data sets have been derived from the NOAA-9 and NOAA-11 SBUV/2 irradiance data sets using both discrete scan measurements about the Mg II line and continuous scan (sweep) measurements over the UV spectrum from 160–400 nm. This paper will discuss the rationale behind the creation of the different Mg II index products, and make a quantitative assessment of the differences between these products. Recommendations for future use of the Mg II index will also be presented.