The crucial role of surface magnetic fields for stellar dynamos: epsilon Eridani, 61 Cygni A, and the Sun

Vol. 661
7. Stellar structure and evolution

The crucial role of surface magnetic fields for stellar dynamos: epsilon Eridani, 61 Cygni A, and the Sun

byS. V. Jeffers, R. H. Cameron, S. C. Marsden, et al. 2022, A&A, 661, A152

The solar magnetic activity has a period of about 11 years, and its spatial-temporal structure has been well established and can be explained by the solar dynamo model. Whether the dynamo model can explain the magnetic activities of other stars remains unclear. In other words, are solar and stellar dynamos similar? With a Zeeman-Doppler imaging (ZDI) technique, the authors have reconstructed the evolution of large-scale magnetic field geometry over several decades for two nearby, active, and low-mass K dwarfs: 61 Cygni A and Epsilon Eridani. The derived magnetic butterfly diagram is then compared to the two stars' chromospheric activity (S-index). They found that the dynamo of 61 Cygni A is quite similar to that of the Sun, while Epsilon Eridani represents a more extreme level of the solar dynamo. They conclude that the surface magnetic field plays a crucial role in the dynamos of the three stars, 61 Cyni, Epsilon Eridani, and the Sun.