Spectrum line intensity as a surrogate for solar irradiance variations
Science (New York, N.Y.)
|June 24, 1988
Summary
Active Cavity Radiometer Irradiance Monitor (ACRIM) solar constant measurements confirm solar variability. Ground-based spectrophotometry indicates that solar faculae are the source of irradiance changes, tracking the 11-year solar cycle.
Area of Science:
- Solar Physics
- Radiometry
- Spectroscopy
Background:
- Solar constant measurements are crucial for understanding Earth's climate.
- Variability in solar irradiance has been observed but its sources require further investigation.
Purpose of the Study:
- To compare Active Cavity Radiometer Irradiance Monitor (ACRIM) solar constant data with ground-based irradiance spectrophotometry.
- To independently confirm the variability of ACRIM solar irradiance measurements.
- To identify the solar features responsible for irradiance variations.
Main Methods:
- ACRIM solar constant measurements (1980-1986) were compared with ground-based spectrophotometry of Fraunhofer lines.
- Both datasets were smoothed using an 85-day running mean.
- ACRIM total solar irradiance (S) values were corrected for sunspot blocking (S(c)).
Main Results:
- The strength of the manganese 539.4 nm line showed near-perfect correlation with ACRIM S(c) values.
- Other spectral features from the photosphere and chromosphere also tracked well with ACRIM data.
- These findings independently confirm the ACRIM solar irradiance variability.
Conclusions:
- Solar faculae are identified as the primary source of irradiance variability.
- ACRIM solar irradiance measurements accurately reflect the 11-year solar activity cycle.
- The study validates the ACRIM instrument's ability to monitor solar irradiance changes.
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