# Multi-frequency scatter broadening evolution of pulsars - I

## TL;DR

This study analyzes scatter broadening of 47 pulsars across multiple frequencies to understand interstellar medium turbulence, providing new estimates of the frequency scaling index for most pulsars and revealing diverse turbulence characteristics.

## Contribution

It offers the first comprehensive multi-frequency analysis of scatter broadening for 39 pulsars, significantly expanding the sample with new $oldsymbol{ extit{ ext{alpha}}}$ estimates and insights into ISM turbulence.

## Key findings

- 65% of pulsars have flatter $ extit{ ext{alpha}}$ than Kolmogorov prediction.
- Flatter $ extit{ ext{alpha}}$ correlates with higher turbulence levels $C^{2}_{n_e}$.
- $ extit{ ext{alpha}}$ varies with dispersion measure, indicating diverse turbulence along lines of sight.

## Abstract

We present multi-wavelength scatter broadening observations of 47 pulsars, made with the Giant Metre-wave Radio Telescope (GMRT), Ooty Radio Telescope (ORT) and Long Wavelength Array (LWA). The GMRT observations have been made in the phased array mode at 148, 234, and 610 MHz and the ORT observations at 327 MHz. The LWA data sets have been obtained from the LWA pulsar data archive. The broadening of each pulsar as a function of observing frequency provides the frequency scaling index, $\alpha$. The estimations of $\alpha$ have been obtained for 39 pulsars, which include entirely new estimates for 31 pulsars. This study increases the total sample of pulsars available with $\alpha$ estimates by $\sim$50\%. The overall distribution of $\alpha$ with the dispersion measure (DM) of pulsar shows interesting variations, which are consistent with the earlier studies. However, for a given value of DM a range of $\alpha$ values are observed, indicating the characteristic turbulence along each line of sight. For each pulsar, the estimated level of turbulence, $C^{2}_{n_e}$, has also been compared with $\alpha$ and DM. Additionally, we compare the distribution of $\alpha$ with the theoretically predicated model to infer the general characteristics of the ionized interstellar medium (ISM). Nearly 65\% of the pulsars show a flatter index (i.e., $\alpha < 4.4$) than that is expected from the Kolmogorov turbulence model. Moreover, the group of pulsars having flatter index is typically associated with an enhanced value of $C^{2}_{n_e}$ than those with steeper index.