Modeling Nonaxisymmetric Bow Shocks: Solution Method and Exact Analytic Solutions
Modeling Nonaxisymmetric Bow Shocks: Solution Method and Exact Analytic Solutions
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非轴对称弓激波建模：求解方法和精确解析解
DOI：
10.1086/308576
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
F. Wilkin
中科院分区：
文献类型：
--
作者：
F. Wilkin
针对薄壳极限下的稳态、动量守恒、非轴对称弓形激波和碰撞风，提出了一种新的求解方法。这是先前公式的概括，包括震前环境介质中的密度梯度以及震前风中的各向异性。对于风未加速的情况，形式主义会产生精确的解析解。提出了两种弓激波情况的解决方案：（1）由于恒星相对于密度梯度垂直于恒星速度的环境介质进行超音速运动，以及（2）由于恒星在均匀介质中移动时具有未对准的轴对称风。在相当一般的情况下还表明，弓激波中的能量热化总速率与风不对称的细节无关，包括非轴对称驱动风的方向，前提是风是非加速且点对称的。该解决方案的一个典型特征是，远离点附近的区域是倾斜的，使得星形不会沿着与远离区域拟合的抛物线的平分线分布。这项工作的主要用途是推断弓激波不对称的起源，无论是由于风还是环境介质或两者兼而有之。
A new solution method is presented for steady state, momentum-conserving, nonaxisymmetric bow shocks and colliding winds in the thin-shell limit. This is a generalization of previous formulations to include a density gradient in the preshock ambient medium as well as anisotropy in the preshock wind. For cases where the wind is unaccelerated, the formalism yields exact, analytic solutions. Solutions are presented for two bow shock cases: (1) that due to a star moving supersonically with respect to an ambient medium with a density gradient perpendicular to the stellar velocity, and (2) that due to a star with a misaligned, axisymmetric wind moving in a uniform medium. It is also shown under quite general circumstances that the total rate of energy thermalization in the bow shock is independent of the details of the wind asymmetry, including the orientation of the nonaxisymmetric driving wind, provided the wind is nonaccelerating and point-symmetric. A typical feature of the solutions is that the region near the standoff point is tilted so that the star does not lie along the bisector of a parabolic fit to the standoff region. The principal use of this work is to infer the origin of bow shock asymmetries, whether due to the wind or ambient medium or both.