FRBs as a tool for uncovering the properties of extragalactic plasma

The interaction of Fast Radio Burst (FRB) radio waves with the intervening plasma between us and the sources is viewed, at times, as a nuisance for probing intrinsic FRB properties. At the same time, it offers unique ways to probe interstellar matter at large redshifts and the intervening intergalactic medium. I will show that FRBs are a promising and unique tool for exploring the H reionization history of the Universe. In addition, due to multi-path propagation, a magnetized plasma screen can cause temporal broadening of the FRB, lightcurve variability, spectral decoherence, depolarization, induced circular polarization and image broadening. I will describe how these different properties are directly inter-related, how they manifest in FRB and pulsar observations, how this can already be used to constrain the nature of the intervening plasma in some bursts and how it affects lensing prospects of FRBs.