标题： 低于劳仑兹尺度的磁场辐射 显示英文标题

标题： Radiation from sub-Larmor scale magnetic fields

摘要： 强磁场的自发快速增长在从天体物理源（例如伽马射线暴和相对论激波）、磁重联到激光等离子体相互作用实验室实验的高能密度环境中相当普遍，在这些环境中它们由Weibel型动能流不稳定产生。 在这些亚拉莫尔尺度的磁场中传播的相对论电子以颤动机制辐射，在这种情况下，磁场的各向异性和粒子分布对产生的辐射有很强的影响。 在这里我们发展了颤动辐射的一般理论，其中包括（i）各向异性磁场和电子速度分布，（ii）捕获电子的影响以及（iii）将描述扩展到辐射粒子的大偏转角，从而在经典颤动和同步辐射机制之间建立了交叉点。 我们的结果与经典Weibel不稳定性粒子模拟获得的辐射光谱惊人地一致。 特别有趣的是磁场增长的起始阶段，当由于捕获群体占主导地位时，瞬态硬同步辐射违反光谱很常见。 这种效应可以作为天体物理源和实验室实验中剧烈磁场增长的独特观测标志。 同样有趣的是，具有小尺度场的系统往往趋于演化为小角度颤动机制，在某些条件下，这种机制可以支配源的整体发射。 显示英文摘要

摘要： Spontaneous rapid growth of strong magnetic fields is rather ubiquitous in high-energy density environments ranging from astrophysical sources (e.g., gamma-ray bursts and relativistic shocks), to reconnection, to laser-plasma interaction laboratory experiments, where they are produced by kinetic streaming instabilities of the Weibel type. Relativistic electrons propagating through these sub-Larmor-scale magnetic fields radiate in the jitter regime, in which the anisotropy of the magnetic fields and the particle distribution have a strong effect on the produced radiation. Here we develop the general theory of jitter radiation, which includes (i) anisotropic magnetic fields and electron velocity distributions, (ii) the effects of trapped electrons and (iii) extends the description to large deflection angles of radiating particles thus establishing a cross-over between the classical jitter and synchrotron regimes. Our results are in remarkable agreement with the radiation spectra obtained from particle-in-cell simulations of the classical Weibel instability. Particularly interesting is the onset of the field growth, when the transient hard synchrotron-violating spectra are common as a result of the dominant role of the trapped population. This effect can serve as a distinct observational signature of the violent field growth in astrophysical sources and lab experiments. It is also interesting that a system with small-scale fields tends to evolve toward the small-angle jitter regime, which can, under certain conditions, dominate the overall emission of a source.