CONTRAST OF FACULAE NEAR THE DISK CENTER AND SOLAR VARIABILITY

We analyze simultaneous, or near-simultaneous, coregistered, digital, photometric images of solar photospheric intensity and line-of-sight m agnetic field. Images were made with the Lockheed tunable filter instr ument at the Swedish Solar Observatory, La Palma, with the video spect ra-spectroheliograph system at the San Fernando Observatory and with t he new NASA spectromagnetograph at the National Solar Observatory at K itt Peak. We study the disk center contrasts of small magnetic element s. While active region faculae are dark at disk center quiet Sun netwo rk features are bright. The populations of magnetic field elements tha t make up these two kinds of features are quite different. Different c ontrast center-limb functions must be used when estimating their irrad iance or luminosity contributions. The disk center contrasts of active region faculae are color dependent and indicate a depth effect relate d to the H- opacity of the facular atmosphere. This result is importan t for calibration of monochromatic observations of faculae to bolometr ic irradiance fluctuations. We emphasize the value of cooperative obse rvations among installations whose differing strengths are complementa ry.