Decoupling Solar Variability and Instrument Trends Using the Multiple Same-Irradiance-Level (MuSIL) Analysis...

Area of Science:

• * Solar Physics
• * Earth Science
• * Atmospheric Science

Background:

• * Solar spectral irradiance (SSI) is crucial for understanding Earth's energy balance and Sun-Earth interactions.
• * Long-term SSI variations, especially over the 11-year solar cycle, are vital for climate and atmospheric research.
• * Previous satellite SSI measurements (since the 1970s) were limited by uncertainties in instrument degradation corrections.

Purpose of the Study:

• * To differentiate solar cycle variability from instrumental trends in SSI data from the Solar Radiation and Climate Experiment (SORCE) and Thermosphere, Mesosphere, Ionosphere, Energetic, and Dynamics (TIMED) missions.
• * To develop and apply a novel technique for more accurate SSI trend analysis.

Main Methods:

• * Developed and applied the Multiple Same-Irradiance-Level (MuSIL) analysis technique.
• * MuSIL analyzes SSI time series at various solar activity levels to identify long-term trends.
• * Applied MuSIL to SORCE (2003-present) and TIMED (2002-present) SSI records across 27-1600 nm.

Main Results:

• * The MuSIL technique identified downward trends in SSI records, likely due to uncorrected instrument degradation.
• * New solar cycle variability results were obtained for SSI between 27 nm and 1600 nm.
• * The technique showed an estimated relative uncertainty of about 5% of the measured solar cycle variability.

Conclusions:

• * The MuSIL analysis provides more accurate SSI variability data by separating solar cycle effects from instrumental issues.
• * This advancement enhances the reliability of SSI records for climate and space weather research.
• * Validation against the total solar irradiance (TSI) record and across different solar cycles confirms the technique's robustness.