Unraveling long-term solar variability and its impact on space climate: The stars as suns project

Abstract. It is well-known that solar variability influences the near-Earth Space environment at short timescales of days- an effect collectively termed as Space Weather. A lesser known and more subtle influence of solar variability at longer timescales is however just beginning to be appreciated. This long-term solar forcing, which is sometimes referred to as Space Climate, has important consequences for the formation and evolution of planetary atmospheres and the evolution of life and global climate on Earth. Understanding the Sun's variability and its heliospheric influence at such scales stretching from millennia to stellar evolutionary timescales is therefore of fundamental importance and a very promising area of future research. However, our understanding of this variability, which is in part connected to the evolution of the solar magnetic dynamo, is limited by continuous sunspot observations, which exist only from the early 17th Century onwards. In this paper we review the “Stars as Suns ” project- in which we take a radically new approach to unraveling long-term solar variability through theoretical modeling and magnetic activity observations of Sun-like stars, which are at various evolutionary phases relative to the Sun