# Scattering study of Pulsars below 100 MHz using LWA1

## TL;DR

This study investigates interstellar scattering effects on pulsar signals below 100 MHz using LWA1, analyzing scattering indices and DM variations over three years to understand ISM structure and scattering models.

## Contribution

It provides new low-frequency scattering measurements for nearby pulsars, testing the thin screen model and exploring the ISM's small-scale structure.

## Key findings

- Scattering spectral index varies across pulsars and over time.
- Observed indices often below theoretical predictions, indicating complex scattering mechanisms.
- Results support the presence of anisotropic or non-thin screen scattering processes.

## Abstract

Interstellar scattering causes pulsar profiles to grow asymmetrically, thus affecting the pulsar timing residuals, and is strongest at lower frequencies. Different Interstellar medium models predict different frequency ($\nu$) and dispersion measure (DM) dependencies for the scattering time-scale $\tau_{sc}$. For Gaussian inhomogeneity the expected scaling relation is $\tau_{sc} \propto \nu^{-4}\ DM^{2}$, while for a Kolmogorov distribution of irregularities, the expected relation is $\tau_{sc} \propto \nu^{-4.4}\ DM^{2.2}$. Previous scattering studies show a wide range of scattering index across all ranges of DM. A scattering index below 4 is believed to be either due to limitations of the underlying assumptions of the thin screen model or an anisotropic scattering mechanism. We present a study of scattering for seven nearby pulsars (DM $< 50$ pc cm$^{-3}$) observed at low frequencies ($10-88$ MHz), using the first station of the Long Wavelength Array (LWA1). We examine the scattering spectral index and DM variation over a period of about three years. The results yield insights into the small-scale structure of ISM as well as the applicability of the thin screen model for low DM pulsars.