EDP Sciences
Free access
Volume 427, Number 3, December I 2004
Page(s) 1031 - 1043
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20041313

A&A 427, 1031-1043 (2004)
DOI: 10.1051/0004-6361:20041313

Comparison between KPVT/SPM and SoHO/MDI magnetograms with an application to solar irradiance reconstructions

T. Wenzler1, S. K. Solanki2, N. A. Krivova2 and D. M. Fluri1

1  Institute of Astronomy, ETH Zentrum, 8092 Zurich, Switzerland
    e-mail: wenzler@astro.phys.ethz.ch
2  Max-Planck-Institut für Sonnensystemforschung (Previously Max-Planck-Institut für Aeronomie.) , 37191 Katlenburg-Lindau, Germany
    e-mail: solanki@linmpi.mpg.de

(Received 18 May 2004 / Accepted 23 July 2004)

To be able to use both space- and ground-based solar magnetograms and construct long time series of derived parameters it is important to cross-calibrate them so that we can estimate their reliability and combine them. Using two different techniques, we compare magnetograms as well as continuum images recorded by the Spectropolarimeter (SPM) on Kitt Peak and the Michelson Doppler Interferometer (MDI) on board SoHO. We find that the result obtained depends on the method used. The method we favour gives almost identical umbral and penumbral areas and very similar total magnetic fluxes in faculae. The magnetic fluxes in umbrae and penumbrae returned by the two instruments, however, differ considerably. We also demonstrate that SPM data can be employed to reconstruct total solar irradiance variations with almost the same accuracy as recently shown for MDI data.

Key words: Sun: solar-terrestrial relations -- methods: data analysis -- Sun: activity -- Sun: faculae, plages -- Sun: magnetic fields -- Sun: sunspots

© ESO 2004