Recently Observed Solar Cycle Spectral Variations and their Modeling

Juan Fontenla (LASP)

A summary of the first accurate solar spectral irradiance (SSI) observations that were obtained by SORCE/SIM instrument since 2004 will be presented. It will be shown that these and UV SSI solar rotation variations can be explained and modeled by the usual activity features identified on the disk. However, such modeling does not explain the solar cycle trends, even if changes in the solar network are included but the inter-network radiance is assumed to remain constant. The observed trends over most of the visible and IR are in opposition to those at most wavelengths shorter than ~400 nm, and follow an interesting pattern when compared to the brightness temperature corresponding to the SSI. This was not expected from the previous models of SSI variations over the solar cycle, and produces a cancelling effect between UV and visible variations in which the total solar irradiance (TSI) variation is only the residual of such cancellation. A plausible explanation for these effects will be presented. Also, consequences of these observations for helioseismic, solar analogs, solar cycle and dynamo, and solar influence on Earth climate studies will be briefly explored.

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