Description
The Sun is approaching a transition in magnetic activity that has been observed in many of its siblings. Sun-like stars sustain magnetism by dynamo-action, powered by the interplay of convection and rotation. Stellar magnetic fields enable the heating of their atmospheres to millions of degrees and drive magnetised stellar winds. These winds play a crucial role in the evolution of Sun-like stars by removing angular momentum during the main sequence, a process called magnetic braking. This causes Sun-like stars to gradually spin down from a few days to around a month. The Sun’s rotation period of 25.4 days and age of 4.6 billion years is near to where magnetized stellar winds appear to become less efficient, a state referred to as weakened magnetic braking. Given that a star’s rotational history is linked to its magnetic activity through dynamo-action, this transition in magnetic braking has implications for how we understand the long-term evolution of exoplanetary atmospheres. However, studying older Sun-like stars is challenging because they are faint, leading to a lack of observational constraints, particularly in terms of rotation period measurements from missions like Kepler/K2 and TESS. Despite these challenges, we have now entered a golden age for solar exploration, with missions such as NASA’s Parker Solar Probe and ESA’s Solar Orbiter providing new insights on the Sun and the solar wind. These missions enable us to better understand the Sun’s present-day magnetic braking which in turn informs rotation-evolution modelling and helps place the Sun in context with its siblings.
