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A&A 382, 678-687 (2002)
DOI: 10.1051/0004-6361:20011666

An evaluation of the correlation between open solar flux and total solar irradiance

M. Lockwood

Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, UK Department of Physics and Astronomy, University of Southampton, Southampton, Hampshire, UK

(Received 1 October 2001 / Accepted 22 November 2001 )

Abstract
The correlation between the coronal source flux F_S and the total solar irradiance I_TS is re-evaluated in the light of an additional 5 years' data from the rising phase of solar cycle 23 and also by using cosmic ray fluxes detected at Earth. Tests on monthly averages show that the correlation with F_S deduced from the interplanetary magnetic field (correlation coefficient, r = 0.62) is highly significant (99.999%), but that there is insufficient data for the higher correlation with annual means ( r = 0.80) to be considered significant. Anti-correlations between I_TS and cosmic ray fluxes are found in monthly data for all stations and geomagnetic rigidity cut-offs ( r ranging from -0.63 to -0.74) and these have significance levels between 85% and 98%. In all cases, the fit is poorest for the earliest data (i.e., prior to 1982). Excluding these data improves the anticorrelation with cosmic rays to r = -0.93 for one-year running means. Both the interplanetary magnetic field data and the cosmic ray fluxes indicate that the total solar irradiance lags behind the open solar flux with a delay that is estimated to have an optimum value of 2.8 months (and is within the uncertainty range 0.8-8.0 months at the 90% level).

Key words: Sun: magnetic fields -- fundamental parameters -- solar-terrestrial relations -- interplanetary medium

© ESO 2002

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