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

大多数巨星都是从最初大约一到几个太阳质量的恒星进化而来的。现代观测技术打开了测量和绘制巨人表面磁场的大门。其中一些显示出相对较强的磁场，但起源不明。第二个观测发现与它们核心的旋转有关。由于这些恒星在恒星演化成巨星时会缩小，它们的旋转速度应该比通过星震学观察到的快数百倍。该项目的主要重点是在巨星的巨大对流包层中产生磁场，以及从核心中消除角动量的效果。将研究对流包层中的湍流发电机以及磁通量进入核心的运输。或者，中等质量恒星的对流核心，当在主序星上时，可能会留下残留场的巨星辐射核心。核心领域的不稳定性进行了分析，这可能会引起增强的角动量输运介导的核心的旋转速率。该项目的主要目标是首次对红巨星从对流包层到内核的磁场的产生和稳定性进行统一的观察，以了解角动量在不同演化阶段的传输。

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.