Observations of Solar Variability Using the SORCE SIM Spectrometer

Jerald Harder, Juan Fontenla, Thomas Woods (LASP)

The Spectral Irradiance Monitor (SIM) on-board the Solar Radiation and Climate Experiment (SORCE) satellite provides the first comprehensive measurements of solar spectral irradiance (SSI) variability from 200-2400 nm, accounting for about 97% of the total solar irradiance (TSI) incident at the top of the Earth’s atmosphere. SIM observations indicate that, in addition to modulation due to active region passage, the SSI values for wavelengths with a brightness temperature greater than 5770 K show a brightening with decreasing solar activity, whereas below this value there is a dimming. We will show these results over the last 5+ years of the mission during the descending phase of Solar Cycle 23 that includes the current solar minimum time period and discuss our methods of performing degradation corrections, a critical aspect to the interpretation of the long term trends observed by the instrument.

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