Amplification of OAM radiation by astrophysical masers
Amplification of OAM radiation by astrophysical masers
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DOI：
10.1093/mnras/stu1947
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发表时间：
2014-12-21
影响因子：
4.8
通讯作者：
Schemmel, P.
中科院分区：
文献类型：
--
作者：
Gray, M. D.;Pisano, G.;Schemmel, P.
我们扩展的天体物理脉泽传播理论通过介质与塞曼分裂分子响应的情况下，一个不均匀的磁场，并允许在传播方向的辐射的电场分量：辐射与轨道角动量的特性。一个经典的减少的控制方程导致一组九个微分方程的强度一样的参数为每个傅立叶分量的辐射的演变。这些参数中的四个对应于标准斯托克斯参数，而其他五个代表电场的z分量及其与x-y平面中的常规分量的耦合。控制方程的一个限制性的解析解证明了斯托克斯参数与轨道角动量的非平凡耦合：电场的z分量可以从只有斯托克斯-I非零的背景中增长。控制方程的数值解揭示了辐射模式的径向和角结构的情况下，一个理想的四极磁场垂直于传播方向。在这种理想情况下，辐射轨道角动量的产生，如偏振，可以接近100%。
We extend the theory of astrophysical maser propagation through a medium with a Zeeman-split molecular response to the case of a non-uniform magnetic field, and allow a component of the electric field of the radiation in the direction of propagation: a characteristic of radiation with orbital angular momentum. A classical reduction of the governing equations leads to a set of nine differential equations for the evolution of intensity-like parameters for each Fourier component of the radiation. Four of these parameters correspond to the standard Stokes parameters, whilst the other five represent the z-component of the electric field, and its coupling to the conventional components in the x-y-plane. A restricted analytical solution of the governing equations demonstrates a non-trivial coupling of the Stokes parameters to those representing orbital angular momentum: the z-component of the electric field can grow from a background in which only Stokes-I is non-zero. A numerical solution of the governing equations reveals radiation patterns with a radial and angular structure for the case of an ideal quadrupole magnetic field perpendicular to the propagation direction. In this ideal case, generation of radiation orbital angular momentum, like polarization, can approach 100 per cent.