Magnetic activity in late-type giant stars: Numerical MHD simulations of non-linear dynamo action in Betelgeuse

Bertil Dorch (1)

1 NBI - Niels Bohr Institute [Copenhagen]

Evidence is presented from numerical magneto-hydrodynamical simulations for the existence of magnetic activity in late-type giant stars. A red supergiant with stellar parameters similar to that of Betelgeuse (α Orionis) is modeled as a "star-in-a-box" with the high-order "Pencil Code". Both linear kinematic and non-linear saturated dynamo action are possible: the non-linear magnetic field saturates at a super-equipartition value corresponding to surface magnetic field of field strengths up to ~500 Gauss. In the linear regime two different modes of dynamo action are found with exponential growth rates of ~4 and 25 years, respectively. It is speculated that magnetic activity of late-type giants may influence dust and wind formation and possibly lead to the heating of the outer atmospheres of these stars.

Mots clés: stars: AGB and post-AGB; stars: late-type; stars: activity; stars: individual: Betelgeuse; stars: magnetic fields; magnetohydrodynamic: (MHD)

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]

Bertil Dorch. Magnetic activity in late-type giant stars: Numerical MHD simulations of non-linear dynamo action in Betelgeuse. Astronomy and Astrophysics - A&A, 2004, 423 (3), pp.1101. ⟨10.1051/0004-6361:20040435⟩. ⟨hal-00165889⟩