The Contribution of Components of Magnetic Activity to Variations in Solar Irradiance

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Session 123 -- Solar Magnetic Field and Solar Variabilty
Oral presentation, Thursday, 12, 1995, 2:00pm - 3:30pm

[123.09] The Contribution of Components of Magnetic Activity to Variations in Solar Irradiance

Karen L. Harvey (SPRC), Oran R. White (HAO)

The evolution of magnetic fields on the solar surface is the principal underlying cause of variations observed in the radiative output of the Sun. These magnetic fields are manifested in a wide range of structures from large active regions with sunspots to small-scale network elements. In this paper, we address the identification and separation of the different components of solar magnetic surface activity in digitally-recorded full-disk magnetograms. Such quantitative identification provides a tool in learning how the magnetic field distribution on the visible solar hemisphere effects variability of the solar radiation received at the earth.

Full-disk, high-resolution magnetograms from the National Solar Observatory are the input to a logic chain that defines several classes of magnetic structures: active regions (plage, sunspots), decaying active regions (active network), and weak and quiet network. The analysis technique employs several criteria based on size of the region, its polarity, its maximum and mean field strength, the magnetic filling factor, and association with sunspots to differentiate and categorize these magnetic structures and to create image masks that isolate these structure classes in both magnetograms or spectral intensity images, such as Ca II K and He I 10830 spectroheliograms. The final products are the image masks defining the detailed geometrical shape on the visible solar hemisphere plus a table of numerical parameters summarizing the properties of each individual magnetic region. This physical classification is then used to investigate the pixel-by-pixel relation between the observed longitudinal component of the magnetic field in the different magnetic structures and the strength of emission lines showing chromospheric variability. We will show our progress in defining how each type of solar magnetic structure contributes the variability of the Sun's radiative output at two epochs in Solar Cycle 22, Jan-Feb 1992 and Jun-Jul 1993. Our analysis addresses variability on solar rotation time scales as well as the slower change from maximum conditions in 1992 to moderate levels of activity in 1993.

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