Empirical Modeling of Radiative <Emphasis Type="Italic">versus</Emphasis> Magnetic Flux for the Sun-as-a-Star |
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| Authors: | Dora Preminger Dibyendu Nandy Gary Chapman Petrus C H Martens |
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| Institution: | 1.San Fernando Observatory,California State University,Northridge,USA;2.Department of Physical Sciences,Indian Institute of Science Education and Research, Kolkata,Mohanpur,India;3.Harvard-Smithsonian Center for Astrophysics,Cambridge,USA;4.Physics Department,Montana State University,Bozeman,USA |
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| Abstract: | We study the relationship between full-disk solar radiative flux at different wavelengths and average solar photospheric magnetic-flux
density, using daily measurements from the Kitt Peak magnetograph and other instruments extending over one or more solar cycles.
We use two different statistical methods to determine the underlying nature of these flux – flux relationships. First, we
use statistical correlation and regression analysis and show that the relationships are not monotonic for total solar irradiance
and for continuum radiation from the photosphere, but are approximately linear for chromospheric and coronal radiation. Second,
we use signal theory to examine the flux – flux relationships for a temporal component. We find that a well-defined temporal
component exists and accounts for some of the variance in the data. This temporal component arises because active regions
with high magnetic-field strength evolve, breaking up into small-scale magnetic elements with low field strength, and radiative
and magnetic fluxes are sensitive to different active-region components. We generate empirical models that relate radiative
flux to magnetic flux, allowing us to predict spectral-irradiance variations from observations of disk-averaged magnetic-flux
density. In most cases, the model reconstructions can account for 85 – 90% of the variability of the radiative flux from the
chromosphere and corona. Our results are important for understanding the relationship between magnetic and radiative measures
of solar and stellar variability. |
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