A 10-YEAR SET OF CA-II-K-LINE FILTERGRAMS

We have processed a 10-year set of BBSO Ca II K-line filtergrams cover ing most of solar cycle 22. The excess K-line emission is integrated t o form linear and square-root activity indices that are fitted to UV d ata from UARS and SME. Good fits are found both for the Mg II core-win g ratio (linear) and total L alpha irradiance (square root) and the in dices are thus good proxies for UV data. The SME L alpha irradiance is systematically lower by 20% than predicted from our corresponding K-l ine indices. The 10.7 cm radio data confirms that SME underestimated t he Bur. The network is partly responsible for the solar cycle variatio n of the indices and is relatively more important in La than in Mg II and Ca II K. This is due to the saturation of L alpha equivalent width . We also report on substantial improvements to the equipment and redu ction software. The system is now based on a digital CCD camera which promises more accurate measurements in the upcoming solar cycle 23.