近日,上海交通大学自然科学研究院、数学科学学院特别研究员魏星在天体物理主流杂志ApJ、ApJL上发表了两篇文章 The Magnetic Effect on Dynamical Tide in Rapidly Rotating Astronomical Objects, Dynamo Induced by Time-periodic Force。第一篇文章研究磁场对动力潮汐的影响,通过数值计算发现磁场可以增加潮汐共振的范围并引起很强的欧姆耗散,而且得到了潮汐耗散关于磁场的标度率,这个工作对理解双星轨道演化以及估算星球内部磁场大小非常有帮助。第二篇文章研究湍流磁流体发电机,通过数值计算发现时间周期的驱动力与惯性波共振时,会引起很强的流动响应,但却抑制了磁场产生,这是由于磁场和流动的非线性耦合,这个违反直觉的发现对理解星球内部湍流产生磁场的过程非常有帮助。

Dr. Xing Wei recently published two papers in ApJ and ApJL. In the ApJ paper, the magnetic tide was numerically studied in spherical geometry and it is found that magnetic field broadens the tidal resonance and destroys the thin shear layers due to propagation of inertial waves and that Ohmic dissipation dominates over viscous dissipation in the astrophysical situation. Moreover, total tidal dissipation scales as square of magnetic field, which can be used to estimate the internal field strength of binary stars. In the ApJL paper, MHD dynamo induced by a time-periodic helical force was numerically studied. It is found that dynamo is generated near the resonance of force frequency and eigen-frequency of inertial waves. Moreover, the dynamo efficiency is suppressed at the exact resonant frequency because of the nonlinear coupling of fluid flow and magnetic field. This is opposite to intuition and is of help to understanding turbulent dynamo.