Abstract
We have extended the proxy relationship between irradiance and microwaves by using the daily solar fluxes from Toyokawa Observatory at 1000, 2000, 3750 and 9400 MHz in addition to the Ottawa 2800 MHz flux for the years 1980–1989. It turns out that the flux at 1000 MHz is better correlated with irradiance than the flux at higher frequencies-an unexpected result. We have also found that the spectrum of the flux shows shape changes that are related to the number and type of active regions. Because of this the five-frequency spectral measurements of microwave flux allow one to separate the sunspot and coronal features, providing an improved proxy of solar variability.
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Schmahl, E.J., Kundu, M.R. Solar cycle variation of the microwave spectrum and total irradiance. Sol Phys 152, 167–173 (1994). https://doi.org/10.1007/BF01473200
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DOI: https://doi.org/10.1007/BF01473200