# Dual-Component Plasma Lens Models

## TL;DR

This paper explores dual-component plasma lens models, revealing complex critical structures and light curves, which enhance understanding of plasma lensing phenomena affecting radio observations and can help interpret extreme scattering events.

## Contribution

It generalizes plasma lens models to dual components, analyzing their critical structures and degeneracies, advancing the modeling of plasma lensing effects in astronomy.

## Key findings

- Dual-component plasma lenses exhibit complex critical and caustic structures.
- Model degeneracies can be broken through close monitoring of scattering events.
- The work maps critical formation based on component separation and size.

## Abstract

In contrast to the converging, achromatic behaviour of axisymmetric gravitational lenses, diverging frequency-dependent lensing occurs from refraction due to a distribution of over-dense axisymmetric plasma along an observer's line of sight. Such plasma lenses are particularly interesting from the point of view of astronomical observations because they can both magnify and dim the appearance of background sources as a function of frequency. Plasma lensing is believed to be involved in a number of separate phenomena involving the scintillation of radio pulsars, extreme scattering events of background radio sources and may also play a role in the generation of fast radio bursts. These lensing phenomena are believed to occur in dense environments, in which there may be many density perturbations between an observer and background source. In this work we generalize individual plasma lens models to produce dual component lenses using families of plasma lens models previously studied in the literature, namely the exponential and softened power-law lenses. Similar to binary gravitational lens models, these dual component plasma lenses feature a rich and complex critical and caustic morphology, as well as generate more complicated light curves. We map the number of criticals formed for a given component separation and angular size, and highlight a relevant degeneracy between two particular models. This work provides an argument in favor of close monitoring of extreme scattering events in progress in order to break such model degeneracies.