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arXiv 1011.2684astro-ph.SR
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不稳定性导致的Ap星的磁场

Magnetic fields of Ap stars as a result of an instability

R. Arlt, G. Ruediger

摘要:

Ap星的磁性通常归因于自恒星的前主序星时代以来没有太大变化的古磁场。稳定的磁场配置是已知的,可能持续整个主序星的生活,但他们可能不会显示的复杂性和多样性所表现出的Ap星观察。我们认为,Ap星的磁性是不是一个稳定的配置的结果,而是一个不稳定的结果,基于强环形磁场埋在恒星。这种高度非轴对称的不稳定性使人想起在Ap星上看到的场的多样性。这些剩余磁场的强度实际上是内部环向场的百分之几到相当大的分数之间;这意味着千高斯量级的磁场强度与观测到的是一致的。表面的磁场出现得相当快;粗略估计的时间尺度为几年。由于旋转稳定了不稳定性,正常的A星可能仍然拥有相当大的,不可见的环形磁场。

英文摘要:

Ap star magnetism is often attributed to fossil magnetic fields which have not changed much since the pre-main-sequence epoch of the stars. Stable magnetic field configurations are known which could persist probably for the entire main-sequence life of the star, but they may not show the complexity and diversity exhibited by the Ap stars observed. We suggest that the Ap star magnetism is not a result of stable configurations, but is the result of an instability based on strong toroidal magnetic fields buried in the stars. The highly nonaxisymmetric remainders of the instability are reminiscent of the diversity of fields seen on Ap stars. The strengths of these remnant magnetic fields is actually between a few per cent up to considerable fractions of the internal toroidal field; this means field strengths of the order of kGauss being compatible with what is observed. The magnetic fields emerge at the surface rather quickly; rough estimates deliver time-scales of the order of a few years. Since rotation stabilizes the instability, normal A stars may still host considerable, invisible toroidal magnetic fields.

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