4.6 Article

Detecting deep axisymmetric toroidal magnetic fields in stars The traditional approximation of rotation for differentially rotating deep spherical shells with a general azimuthal magnetic field

期刊

ASTRONOMY & ASTROPHYSICS
卷 661, 期 -, 页码 -

出版社

EDP SCIENCES S A
DOI: 10.1051/0004-6361/202142956

关键词

magnetohydrodynamics (MHD); waves; stars; rotation; stars; magnetic field; stars; oscillations; methods; analytical

资金

  1. CNES PLATO
  2. Research Foundation Flanders (FWO) [12ZB620N, V414021N]
  3. National Science Foundation [NSF PHY-1748958]
  4. KU Leuven Research Council [C16/18/005: PARADISE]
  5. BELgian federal Science Policy Office (BELSPO)

向作者/读者索取更多资源

The study finds that strong toroidal magnetic fields have an impact on the period spacings of gravity and Rossby modes. An equatorial azimuthal magnetic field with an amplitude of about 10^5 G can be detected in high radial-order modes in gamma Dor and SPB stars. However, more complex hemispheric configurations are more difficult to observe.
Context. Asteroseismology has revealed small core-to-surface rotation contrasts in stars in the whole Hertzsprung-Russell diagram. This is the signature of strong transport of angular momentum (AM) in stellar interiors. One of the plausible candidates to efficiently carry AM is magnetic fields with various topologies that could be present in stellar radiative zones. Among them, strong axisymmetric azimuthal (toroidal) magnetic fields have received a lot of interest. Indeed, if they are subject to the so-called Tayler instability, the accompanying triggered Maxwell stresses can transport AM efficiently. In addition, the electromotive force induced by the fluctuations of magnetic and velocity fields could potentially sustain a dynamo action that leads to the regeneration of the initial strong axisymmetric azimuthal magnetic field. Aims. The key question we aim to answer is whether we can detect signatures of these deep strong azimuthal magnetic fields. The only way to answer this question is asteroseismology, and the best laboratories of study are intermediate-mass and massive stars with external radiative envelopes. Most of these are rapid rotators during their main sequence. Therefore, we have to study stellar pulsations propagating in stably stratified, rotating, and potentially strongly magnetised radiative zones, namely magneto-gravito-inertial (MGI) waves. Methods. We generalise the traditional approximation of rotation (TAR) by simultaneously taking general axisymmetric differential rotation and azimuthal magnetic fields into account. Both the Coriolis acceleration and the Lorentz force are therefore treated in a non-perturbative way. Using this new formalism, we derive the asymptotic properties of MGI waves and their period spacings. Results. We find that toroidal magnetic fields induce a shift in the period spacings of gravity (g) and Rossby (r) modes. An equatorial azimuthal magnetic field with an amplitude of the order of 10(5) G leads to signatures that are detectable in period spacings for high-radial-order g and r modes in gamma Doradus (gamma & x2006;Dor) and slowly pulsating B (SPB) stars. More complex hemispheric configurations are more difficult to observe, particularly when they are localised out of the propagation region of MGI modes, which can be localised in an equatorial belt. Conclusions. The magnetic TAR, which takes into account toroidal magnetic fields in a non-perturbative way, is derived. This new formalism allows us to assess the effects of the magnetic field in gamma Dor and SPB stars on g and r modes. We find that these effects should be detectable for equatorial fields thanks to modern space photometry using observations from Kepler, TESS CVZ, and PLATO.

作者

我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。

评论

主要评分

4.6
评分不足

次要评分

新颖性
-
重要性
-
科学严谨性
-
评价这篇论文

推荐

暂无数据
暂无数据