Special Relativistic Magnetohydrodynamic Simulation of Two-Component Outflow Powered by Magnetic Explosion on Compact Stars
Special Relativistic Magnetohydrodynamic Simulation of Two-Component Outflow Powered by Magnetic Explosion on Compact Stars
复制标题
致密星磁爆炸驱动的二分量流出的狭义相对论磁流体动力学模拟
DOI：
10.1088/0004-637x/733/1/18
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
K.
中科院分区：
文献类型：
--
作者：
Matsumoto;J.;Masada;Y.;Asano;E.;Shibata;K.
采用相对论磁流体动力学方法研究了致密星星表面磁爆炸驱动外流的非线性动力学行为。作为初始平衡态，我们采用了一个球形恒星物体，它嵌入在密度为ρ（r）<$r− α的流体静力等离子体中，并被偶极磁场穿过。在致密星星表面注入的磁能打破了平衡，引发了双组分外流。在早期演化阶段，恒星表面的磁压迅速增加，引发磁驱动外流。一个强大的前向冲击驱动流出，然后激发。磁驱动外流的膨胀速度由恒星表面的阿尔文速度表征，并遵循一个简单的标度关系v mag v A 1/2。当初始密度分布随半径急剧下降时，强激波在磁驱动分量之前被自相似地加速到相对论速度。我们发现它按照一个自相似关系式Γ sh <$rsh演化，其中Γ sh是在激波表面rsh处测得的等离子体的洛伦兹因子。一个纯粹的流体动力学过程将负责的激波驱动外流的加速机制。我们的两分量外流模型是磁爆炸的自然产物，可以更好地理解各种磁化致密星上的磁活动现象。
The nonlinear dynamics of outflows driven by magnetic explosion on the surface of a compact star is investigated through special relativistic magnetohydrodynamic simulations. We adopt, as the initial equilibrium state, a spherical stellar object embedded in hydrostatic plasma which has a density ρ (r)∝ r− α and is threaded by a dipole magnetic field. The injection of magnetic energy at the surface of a compact star breaks the equilibrium and triggers a two-component outflow. At the early evolutionary stage, the magnetic pressure increases rapidly around the stellar surface, initiating a magnetically driven outflow. A strong forward shock driven outflow is then excited. The expansion velocity of the magnetically driven outflow is characterized by the Alfvén velocity on the stellar surface and follows a simple scaling relation v mag∝ v A 1/2. When the initial density profile declines steeply with radius, the strong shock is accelerated self-similarly to relativistic velocity ahead of the magnetically driven component. We find that it evolves according to a self-similar relation Γ sh∝ r sh, where Γ sh is the Lorentz factor of the plasma measured at the shock surface r sh. A purely hydrodynamic process would be responsible for the acceleration mechanism of the shock driven outflow. Our two-component outflow model, which is the natural outcome of the magnetic explosion, can provide a better understanding of the magnetic active phenomena on various magnetized compact stars.