Contribution of the small photospheric magnetic elements to the long-term solar irradiance

We used near-simultaneous full disk magnetograms and images of the photospheric continuum intensity provided by MDI/SOHO to analyze the long-term evolution of the intensity contrast of small magnetic features -faculae and magnetic network- as a function of position, magnetic signal and time, from minimum to maximum of cycle 23. We find that the spectral irradiance characteristics, at 676.8 nm, of the small photospheric magnetic elements are practically invariable throughout the rising phase of solar cycle 23. A preliminary statistical analysis of the magnetic field suggests that the small magnetic elements are likely to provide a significant contribution to the solar cycle irradiance change.