GOES EUVS Magnesium II Index: The beginning of a new climate data record

<p>The GOES-R series spacecraft include a new operational measurement for GOES satellites, the Magnesium II (MgII) core-to-wing index.&#160; This solar activity proxy has been measured at a daily cadence beginning in 1978.&#160; It is widely used in solar spectral irradiance models such as the NRLSSI CDR (Coddington et al. 2016).&#160; The C Chanel of the Extreme and Ultraviolet Spectrograph (EUVSC) on GOES 16 began making operational MgII index measurements at high cadence in early 2017.&#160; There are currently three such instruments in orbit on GOES 16, 17, and 18 as part of the EXIS suite of solar irradiance instruments.&#160; In the past, the MgII index was only measured a few times per day, but EXIS makes measurements at a 3-second cadence to monitor rapid changes in the Sun.</p> <p>In this presentation, we will describe the available data product and how it compares with previous measurements.&#160; On long timescales it can be used to extend the historical record, and on short timescales it reveals solar activity of interest to space weather practitioners.</p>