Plasma microlensing dynamic spectrum probing fine structures in the ionized interstellar medium

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