The exoplanetary magnetosphere extension in Sun-like stars based on the solar wind and solar {UV} emission

The solar activity in form of coronal mass ejections or solar wind disturbances, such as slow or high speed streams, affects the circumterrestrial electromagnetic environment, with a primary effect on the magnetosphere, compressing and perturbing it. Here, in order to connect the long-term solar activity variations to solar wind properties, we use measurement of a proxy for chromospheric activity, the Ca II K index, and solar wind OMNI data for the time interval 1965-2021, which almost entirely covers the last 5 solar cycles. By using both a cross correlation and a mutual information approach, a 3.6-year mean lag has been found between Ca II K index and solar wind dynamic pressure. This result allows us to obtain a relationship between the solar UV emission and the solar wind dynamic pressure, enabling us to derive the Earth’s magnetospheric extension over the last 5 solar cycles. Moreover, the advantage of having used the Ca II K index proxy is that the relation found for the Sun can be easily extended to other stars with similar properties (i.e. Sun-like stars). To this scope, the model is then used to study the effect of stellar wind dynamic pressure on the magnetosphere of Earth-like planets orbiting at 1 AU around a sample of Sun-like stars.