Title: General properties of the radiation spectra from relativistic electrons moving in a Langmuir turbulence Show Chinese title

Title: 相对论电子在朗缪尔湍流中运动时辐射谱的一般性质

Abstract: We examine the radiation spectra from relativistic electrons moving in a Langmuir turbulence expected to exist in high energy astrophysical objects by using numerical method. The spectral shape is characterized by the spatial scale {\lambda}, field strength {\sigma}, and frequency of the Langmuir waves, and in term of frequency they are represented by {\omega}_0 = 2{\pi}c/{\lambda}, {\omega}_st = e{\sigma}/mc, and {\omega}_p, respectively. We normalize {\omega}_st and {\omega}_p by {\omega}_0 as \a \equiv {\omega}_st/{\omega}_0 and \b \equiv{\omega}_p/{\omega}_0, and examine the spectral shape in the a-b plane. An earlier study based on Diffusive Radiation in Langmuir turbulence (DRL) theory by Fleishman and Toptygin showed that the typical frequency is {\gamma}^2{\omega}_p and that the low frequency spectrum behaves as F_{\omega} pronto {\omega}^1 for b > 1 irrespective of a. Here, we adopt the first principle numerical approach to obtain the radiation spectra in more detail. We generate Langmuir turbulence by superposing Fourier modes,inject monoenergetic electrons, solve the equation of motion, and calculate the radiation spectra using Lienard-Wiechert potential. We find different features from the DRL theory for a>b>1. The peak frequency turns out to be {\gamma}^2{\omega}_st which is higher than {\gamma}^2{\omega}_p predicted in the DRL theory, and the spectral index of low frequency region is not 1 but 1/3. It is because the typical deflection angle of electrons is larger than the angle of the beaming cone sim 1/{\gamma}. We call the radiation for this case "Wiggler Radiation in Langmuir turbulence" (WRL). Show Chinese abstract

Abstract: 我们用数值方法研究了预期存在于高能天体物理对象中的朗缪尔湍流中运动的相对论电子的辐射光谱。 谱线形状由空间尺度{\lambda }、场强{\sigma }和朗缪尔波的频率表征，并且用频率表示分别为 {\omega }_0 = 2{\pi }c/{\lambda }、{\omega }_st = e{\sigma }/mc 和{\omega }_p。 我们将{\omega }_st 和{\omega }_p 归一化为{\omega }_0，即\a \equiv {\omega }_st/{\omega }_0 和\b \equiv{\omega} _p/{\omega }_0，并检查 a-b 平面上的光谱形状。 早前基于朗缪尔湍流（Langmuir turbulence）弥散辐射（Diffusive Radiation in Langmuir turbulence, DRL）理论的一项研究由Fleishman和Toptygin完成，研究表明典型频率为{\gamma }^2{\omega }_p，并且低频谱行为表现为 F_{\omega } pronto {\omega }^1，当 b > 1 时，与 a 无关。 在这里，我们采用从第一性原理出发的数值方法以更详细地获取辐射谱。 我们通过叠加傅里叶模式生成朗缪尔湍流，注入单能电子，求解运动方程，并使用Lienard-Wiechert势计算辐射谱。 我们发现，当 a > b > 1 时，与DRL理论相比具有不同的特征。 峰值频率结果为{\gamma }^2{\omega }_st，高于 DRL 理论预测的{\gamma }^2{\omega }_p，而低频区的谱指数不是 1 而是 1/3。 这是因为电子的典型偏转角大于束流锥角 sim 1/{\gamma }。 我们称这种情况下的辐射为“朗缪尔湍流中的摆动辐射”(WRL)。