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| Paper: |
Understanding the Role of Small-Scale Flux in Solar Spectral Irradiance Variation |
| Volume: |
463, 2nd ATST-EAST Workshop in Solar Physics: Magnetic Fields from the Photosphere to the Corona |
| Page: |
65 |
| Authors: |
Rast, M. P.; Harder, J. W. |
| Abstract: |
Global solar spectral irradiance variations depend on changes in
magnetic flux concentrations at the smallest scales. Modeling has
focused on the contributions of magnetic structures in full disk
images as those contributions have strong center-to-limb dependencies,
but these dependencies have never been determined radiometrically;
only the photometric intensity relative to some reference
‘quiet-sun’,1 the magnetic structure
contrast, is measurable with ground based imagery. This is
problematic because unresolved inhomogeneities influence not only the
full-disk structure intensities themselves, but also the quiet-sun
background against which their contrast is measured. We thus argue
that, to understand the physical causes underlying solar spectral
irradiance variations, two fundamental questions must be addressed:
What is the real Iλ (μ) as a function of B in full-disk
images? This can only be answered by imaging the Sun radiometrically
from space, and we propose a Radiometric Solar Imager design. What
governs spectral irradiance changes at sub arc-second scales? This
can be addressed by a combination of high resolution ground based
imaging (ATST-VBI) and three dimensional radiative
magnetohydrodynamic modeling, and we propose a synoptic approach.
Finally, a way to account for the variance introduced by unresolved
substructure in spectral irradiance modeling must be devised. This is
critical, as imaging and modeling at the highest resolutions but over
the full solar disk will likely remain unattainable for some time. |
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