A composite Mg II index spanning from 1978 to 2003

Abstract

[1] The Mg II core-to-wing ratio is a measure of solar chromospheric variability. The Mg II Index, formed by combining various Mg II core-to-wing data sets, has been used in EUV, UV, and total solar irradiance models. It is one of the longest records of solar variability reaching back nearly 25 years. We present a single, continuous time series of the Mg II core-to-wing ratio extending from November 1978 to the present. The Mg II core-to-wing ratio is a measurement that is well suited to the creating of a single time series despite the fact that the seven different instruments measuring the solar flux near 280 nm have different spectral resolutions and sample rates. The Upper Atmosphere Research Satellite (UARS) Solar Ultraviolet Spectral Irradiance Monitor (SUSIM), UARS Solar Stellar Irradiance Comparison Experiment (SOLSTICE), ERS-2/Global Ozone Monitoring Experiment (GOME) and five NOAA solar backscatter ultraviolet data sets were used. Initially, the best data sets were selected to create a time series spanning from 1978 to the present. Then the gaps in the record were filled with data from various other Mg II data sets. Where no alternate data were available, a cubic spline function was used to bridge the missing data. In some cases the data gaps were too long for reasonable spline fits (more than 5 days), and for these gaps the F10.7 cm flux data were scaled to fill the gaps. Thus a continuous, uninterrupted time series of the Mg II core-to-wing ratio was created. The final Mg II time series is compared with other solar activity indices, such as the F10.7, He I 1083, and Sunspot number, to look for trends in the Mg II data.

Modulation of neutral interstellar He, Ne, O in the heliosphere. Survival probabilities and abundances at IBEX

“…The hierarchical set of proxies is based on the chromospheric MgII c/w index available from 1978 as released by LASP (Heath & Schlesinger 1986;Viereck & Puga 1999;Viereck et al 2004), the F10.7 flux released by NOAA and DRAO (Tapping 1987) available from 1947, and the composite Lyman-α flux published by LASP (available from 1947, but based on actual UV observations from mid-1970-ties, with some gaps filled by proxies developed by the LASP team, see Woods et al 2000). As the most reliable proxy we chose the CELIAS/SEM data (Hovestadt et al 1995), which are measurements of the fragments of the solar spectrum responsible for most of the helium ionization.…”

Solar extreme ultraviolet irradiance: Present, past, and future

“…Since the magnitude of the Mg II index depends on the spectral resolution of the measurements, different data sets must be carefully cross-calibrated during periods of overlap. In this way, Viereck et al [2004] [Snow et al, 2005].…”

Comparison of Magnesium II core-to-wing ratio observations during solar minimum 23/24

“…Users of the MgII index will typically want to have all of the measurements scaled to a common reference dataset. The standard method for determining the linear scaling factor is to merely plot one dataset against another during a period of overlapping measurements and fit a line to the result (Viereck & Puga 1999;Viereck et al 2004). For some datasets, the period of overlapping measurements may be fairly brief, but others may have many years of simultaneous daily measurements.…”

“…The goal of this paper is to combine these observations into a single consistent time series that best represents the solar activity. A future paper will link these observations to the prior composite data record described in Viereck et al (2004). That composite covered the years 1978 through 2003.…”