The History of Activity of the Sun and its Rotational Period on the ZAMS

Abstract

The rotation period of the Sun after it reached ZAMS is estimated from the present rotation rate, average X-ray emission flux and average calcium emission flux. Taking into account all existing uncertainties it is concluded that this initial period was within the range 1-9 days, with the most probable value 2-3 days. Possible influence of the solar activity on evolution of life on the Earth is briefly discussed.