Total solar irradiance variations

Total solar irradiance has been monitored from space for nearly two decades . These space-borne observations have established conclusively that total s olar irradiance changes over a wide range of periodicities-from minutes to the 11-year solar cycle. Since the total energy flux of the Sun is the prin cipal driver for all Earth's atmospheric phenomena, the accurate knowledge of the solar radiation received by the Earth and its variations is an extre mely important issue. In this paper we review the long-term variations of t otal solar irradiance during solar cycles 21 and 22. We conclude that, with in the current accuracy and precision of the measurements, the minimum leve l of total solar irradiance is about the same for both solar cycles 21 and 22. (C) 1999 Elsevier Science Ltd. All rights reserved.