Finally, when the star is about to reach the "main sequence" where she spends most of its life, it establishes a stable system in which hydrogen is converted into helium by thermonuclear reactions and a convective core is created again in its centre because of the strongly exothermic nuclear reactions that take place (step 4). The appearance of a dynamo magnetic field generated in this convective central region can then disrupt the initial configuration and result in a tilting of the initial magnetic field.
The magnetic tilt of HD 190073
For the first time, this transition appears to have been observed in a star, HD 190073.
E. Alecian, C. Neiner, S. Mathis, C. Catala, O. Kochukhov, J. Landstreet, the MiMeS collaboration, Astronomy & Astrophysics, vol. 549, L8.
see the arXiv : http://arxiv.org/abs/1301.1804 /