Stability and generation of magnetic fields in red giants: towards a unified picture

• Applicant: Dr. Rainer Arlt
• Subject Area: Astrophysics and Astronomy
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 500190353

Most giant stars evolved from stars of initially about one to a few solar masses. Modern observing technique opened the door to measuring and mapping the magnetic fields on the surfaces of the giants. Some of them show relatively strong magnetic fields of unclear origin. A second observational finding concerns the rotation of their cores. Since those shrink upon the evolution of the stars into giants, they should rotate hundreds of times faster than is observed through asteroseismology. The generation of magnetic fields in the huge convective envelopes of giant stars as well as their effect of removing angular momentum from the cores is the main focus of the project. Turbulent dynamos in the convective envelopes will be studied as well as the transport of magnetic flux into the cores. Alternatively, the convective core of intermediate-mass stars, when on the main sequence, may leave the emerging radiative core of the giant with remnant fields. Instabilities of the core fields are then analyzed, which may give rise to enhanced angular-momentum transport mediating the rotation rates of the cores. The main goal of this project is to arrive for the first time at a unified view of the generation and stability of magnetic fields in red giants, from the convective envelope to the inner core, in order to understand the transport of angular momentum across different evolutionary stages.

• DFG Programme: Research Grants