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Long‐term changes in the solar photosphere associated with changes in the coronal source flux
Author(s) -
Foster S.,
Lockwood M.
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2000gl011995
Subject(s) - sunspot , flux (metallurgy) , physics , astrophysics , coronal hole , photosphere , coronal loop , greenwich , earth's magnetic field , coronal mass ejection , atmospheric sciences , solar cycle , astronomy , solar wind , environmental science , magnetic field , materials science , quantum mechanics , soil science , spectral line , metallurgy
Using sunspot observations from Greenwich and Mount Wilson, we show that the latitudinal spread of sunspot groups has increased since 1874, in a manner that closely mirrors the long‐term (∼100 year) changes in the coronal source flux, F s , as inferred from geomagnetic activity. This latitude spread is shown to be well correlated with the flux emergence rate required by the model of the coronal source flux variation by Solanki et al. [2000]. The time constant for the decay of this open flux is found to be 3.6±0.8 years. Using this value, and quantifying the photospheric flux emergence rate using the latitudinal spread of sunspot groups, the model reproduces the observed coronal source flux variation. The ratio of the 100‐year drift to the solar cycle amplitude for the flux emergence rate is found to be half of the same ratio for F s .