# Predicting Pulsar Scintillation from Refractive Plasma Sheets

## TL;DR

This paper presents a geometric optics model of pulsar scintillation caused by aligned, corrugated plasma sheets in the interstellar medium, predicting observable variations in pulsar signals over time and frequency.

## Contribution

It introduces a simple, parameterized model of ionized plasma sheets that can be constrained with a single observation to explain pulsar scintillation phenomena.

## Key findings

- Overdense sheets produce brighter lensed images than the line-of-sight image.
- Faint lensed images are closer to the pulsar at higher frequencies for underdense sheets.
- Model predicts frequency-dependent image positions based on sheet density.

## Abstract

The dynamic and secondary spectra of many pulsars show evidence for long-lived, aligned images of the pulsar that are stationary on a thin scattering sheet. One explanation for this phenomenon considers the effects of wave crests along sheets in the ionized interstellar medium, such as those due to Alfv\'en waves propagating along current sheets. If these sheets are closely aligned to our line-of-sight to the pulsar, high bending angles arise at the wave crests and a selection effect causes alignment of images produced at different crests, similar to grazing reflection off of a lake. Using geometric optics, we develop a simple parameterized model of these corrugated sheets that can be constrained with a single observation and that makes observable predictions for variations in the scintillation of the pulsar over time and frequency. This model reveals qualitative differences between lensing from overdense and underdense corrugated sheets: Only if the sheet is overdense compared to the surrounding interstellar medium can the lensed images be brighter than the line-of-sight image to the pulsar, and the faint lensed images are closer to the pulsar at higher frequencies if the sheet is underdense, but at lower frequencies if the sheet is overdense.