THE MAGNESIUM II CORE-TO-WING RATIO IS ONE OF THE MOST IMPORTANT PROXIES FOR SOLAR ACTIVITY. IT IS USED TO REPRESENT THE FACULAR CONTRIBUTION IN IRRADIANCE MODELS SUCH AS NRLSSI2 (CODDINGTON ET AL. 2016). DAILY FULL-DISK IRRADIANCE MEASUREMENTS OF THE MGII FEATURE AT 280 NM EXTEND BACK TO THE BEGINNING OF THE SATELLITE ERA IN 1978. CURRENTLY THERE ARE SEVERAL INSTRUMENTS MAKING THESE OBSERVATIONS INCLUDING THE SOLAR RADIATION CLIMATE EXPERIMENT (SORCE). THE MEASUREMENTS WILL CONTINUE INTO THE FUTURE WITH THE RECENTLY-LAUNCHED GOES-16 EXIS AND THE TOTAL SOLAR AND SPECTRAL IRRADIANCE SENSOR-1 (TSIS-1) SCHEDULED FOR LAUNCH IN LATE 2017. IS THERE A WAY TO IMPROVE THE QUALITY OF THIS CRITICAL SOLAR IRRADIANCE VARIABILITY PROXY? WE PROPOSE TO USE SPATIALLY-RESOLVED HIGH SPECTRAL RESOLUTION MGII OBSERVATIONS FROM THE INTERFACE REGION IMAGING SPECTROGRAPH (IRIS) WHICH OVERLAP THE SORCE OBSERVATIONS TO EMPIRICALLY MEASURE THE UNDERLYING SOURCES OF THE VARIATION IN THE PROXY. UNDERSTANDING HOW THE COMPONENTS OF THE IRRADIANCE PROXY VARY WITH THE SOLAR CYCLE COMPARED TO SOLAR SPECTRAL IRADIANCE (SSI) DATASETS FROM SORCE AND TSIS-1 WILL BETTER DEFINE THE RELATIONSHIP BETWEEN THE OBSERVATIONS AND PROXY-MODELED IRRADIANCES. IRIS REGULARLY MAKES A RASTER OBSERVATION OF THE FULL SOLAR DISK TAKING MAGNESIUM II (MG II) SPECTRA AT EACH DWELL POINT. WE WILL USE THE HIGH SPECTRAL RESOLUTION LINE PROFILES FROM IRIS ALONG WITH MAGNETIC FIELD INFORMATION FROM THE SOLAR DYNAMICS OBSERVATORY HELIOSEISMIC AND MAGNETIC IMAGER (SDO/HMI) TO CREATE A DATABASE OF RADIANCE SPECTRA OF VARIOUS MAGNETIC STRUCTURES SUCH AS PLAGE AND ACTIVE NETWORK. USING IRRADIANCE SPECTRA FROM THE SOLAR RADIATION AND CLIMATE EXPERIMENT/SOLAR-STELLAR IRRADIANCE COMPARISON EXPERIMENT (SORCE/SOLSTICE) WE CAN USE THIS DATABASE TO RECONSTRUCT THE OBSERVED IRRADIANCE VARIATION AND THEREFORE GAIN A BETTER UNDERSTANDING OF THE CONTRIBUTION OF THE DIFFERENT MAGNETIC STRUCTURES TO THAT VARIABILITY. OUR GOAL IS TO PRODUCE A QUANTITATIVE MEASUREMENT OF THE CONTRIBUTION OF THE VARIABILITY IN OBSERVED MAGNETIC STRUCTURES TO THE MG II IRRADIANCE PROXY OVER THE SOLAR CYCLE AND DEVELOP AN IMPROVED PROXY FOR IRRADIANCE MODELING. THE DIFFERENCE BETWEEN THE MGII IRRADIANCE PROXY AND THE MAGNETIC FEATURES IS THE FUNDAMENTAL DIFFERENCE BETWEEN THE TWO MOST WIDELY USED IRRADIANCE MODELS: NRLSSI AND SATIRE.