Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dimming of the Mid-20th Century Sun   Advances in understanding of the white light faculae measured at the Royal
Greenwich Observatory from 1874 to 1976 suggest that they offer a more direct
measure of solar brightening by small diameter photospheric magnetic flux tubes
than do chromospheric proxies. Proxies such as the area of Ca K plages, the Mg
index or the microwave flux include many dark photospheric structures as well
as pores and sunspots. Our reconstruction of variation in total solar
irradiance,TSI,based on the faculae indicates that the sun dimmed by almost 0.1
percent in the mid- twentieth century rather than brightening as represented in
previous reconstructions. This dimmimg at the sun's highest activity level
since the seventeenth century is consistent with the photometric behavior
observed in somewhat younger sun like stars. The prolonged TSI decrease may
have contributed more to the cooling of climate between about 1940 and 1970
than present models indicate.

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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: econ