Latitudinal Variation of the Solar Photospheric Intensity

We have examined images from the Precision Solar Photometric Telescope (PSPT) at the Mauna Loa Solar Observatory (MLSO) in search of latitudinal variation in the solar photospheric intensity. Along with the expected brightening of the solar activity belts, we have found a weak enhancement of the mea...

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Bibliographic Details
Published in:The Astrophysical journal 2008-02, Vol.673 (2), p.1209-1217
Main Authors: Rast, Mark P, Ortiz, Ada, Meisner, Randle W
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
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Summary:We have examined images from the Precision Solar Photometric Telescope (PSPT) at the Mauna Loa Solar Observatory (MLSO) in search of latitudinal variation in the solar photospheric intensity. Along with the expected brightening of the solar activity belts, we have found a weak enhancement of the mean continuum intensity at polar latitudes (continuum intensity enhancement similar to 0.1%-0.2%, corresponding to a brightness temperature enhancement of similar to 2.5 K). This appears to be thermal in origin and not due to a polar accumulation of weak magnetic elements, with both the continuum and Ca II K intensity distributions shifted toward higher values with little change in shape from their midlatitude distributions. Since the enhancement is of low spatial frequency and of very small amplitude, it is difficult to separate from systematic instrumental and processing errors. We provide a thorough discussion of these and conclude that the measurement captures real solar latitudinal intensity variations.
ISSN:0004-637X
1538-4357
DOI:10.1086/524655