Gravitational microlensing has become a mature technique for discovering small gravitational lenses in the Universe that are otherwise beyond our detection limits. Similarly, plasma microlensing can help us explore cosmic plasma lenses. Both pulsar scintillation and extreme scattering events of compact radio sources suggest the existence of ∼au-scale plasma lenses in the ionized interstellar medium (IISM), whose astrophysical correspondence remains a mystery. We demonstrate that plasma microlensing events by these plasma lenses recorded in the form of wide-band dynamic spectra are a powerful probe of their nature. Using the recently developed Picard–Lefschetz integrator for the Kirchhoff–Fresnel integral, we simulate such dynamic spectra for a well-motivated family of single-variable plasma lenses. We demonstrate that the size, strength, and shape of the plasma lens can be measured from the location of the cusp point and the shape of spectral caustics, respectively, with a combination of distances and the effective velocity known a priori or measured from the widths of the interference pattern. Future wide-band observations of pulsars, whose plasma microlensing events may be predictable from parabolic arc monitoring, are the most promising ground to apply our results for a deeper insight into the fine structures in the IISM.

中文翻译：

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等离子体微透镜动态光谱探测电离星际介质中的精细结构

引力微透镜已成为一种成熟的技术，用于发现宇宙中超出我们检测极限的小型引力透镜。同样，等离子微透镜可以帮助我们探索宇宙等离子透镜。紧凑型射电源的脉冲星闪烁和极端散射事件都表明在电离星际介质（IISM）中存在~au级等离子体透镜，其天体物理对应仍然是一个谜。我们证明了这些等离子体透镜以宽带动态光谱的形式记录的等离子体微透镜事件是对其性质的有力探测。使用最近开发的用于 Kirchhoff-Fresnel 积分的 Picard-Lefschetz 积分器，我们为动机良好的单变量等离子透镜系列模拟了这种动态光谱。我们证明了尺寸、强度、等离子透镜的形状和形状可以分别从尖点的位置和光谱焦散的形状测量，结合距离和先验已知的有效速度或从干涉图案的宽度测量。脉冲星的未来宽带观测，其等离子体微透镜事件可以通过抛物线弧监测来预测，是应用我们的结果更深入地了解 IISM 中的精细结构的最有希望的基础。