Solar EUV Monitor (SEM) absolute irradiance measurements and how they are affected by choice of reference spectrum

Seth R. Wieman; Darrell L. Judge; Leonid V. Didkovsky

doi:10.1117/12.893163

6 October 2011 Solar EUV Monitor (SEM) absolute irradiance measurements and how they are affected by choice of reference spectrum

Seth R. Wieman, Darrell L. Judge, Leonid V. Didkovsky

Author Affiliations +

Proceedings Volume 8148, Solar Physics and Space Weather Instrumentation IV; 81480G (2011) https://doi.org/10.1117/12.893163
Event: SPIE Optical Engineering + Applications, 2011, San Diego, California, United States

Abstract

The SOHO/CELIAS Solar EUV Monitor (SEM) has measured absolute extreme ultraviolet (EUV) solar irradiance nearly continuously over a 15 year period that includes two solar cycle minima, 22/23 (1996) and 23/24 (2008). Calibration of the SEM flight instrument and verification of the data have been maintained through measurements from a series of sounding rocket calibration underflights that have included a NIST calibrated SEM clone instrument as well as a Rare Gas Ionization Cell (RGIC) absolute detector. From the beginning of SEM data collection in 1996, the SOLERS 22 fixed reference solar spectrum has been used to calculate absolute EUV flux values from SEM raw data. Specifically, the reference spectrum provides a set of weighting factors for determining a weighted average for the wavelength dependent SEM response. The spectrum is used for calculation of the second order contamination in the first order channel signals, and for the comparison between SEM flux measurements with broader-band absolute RGIC measurements. SOHO/SEM EUV flux measurements for different levels of solar activity will be presented to show how the choice of reference spectra now available affects these SEM data. Both fixed (i.e. SOLERS 22) and non-fixed (Solar Irradiance Platform/Solar 2000 and SDO/EVE/MEGS) reference spectra have been included in this analysis.

Citation Download Citation

Seth R. Wieman, Darrell L. Judge, and Leonid V. Didkovsky "Solar EUV Monitor (SEM) absolute irradiance measurements and how they are affected by choice of reference spectrum", Proc. SPIE 8148, Solar Physics and Space Weather Instrumentation IV, 81480G (6 October 2011); https://doi.org/10.1117/12.893163

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