Scatter broadening of pulsars and implications on the interstellar medium turbulence

Abstract

Observations reveal a uniform Kolmogorov turbulence throughout the diffuse ionized interstellar medium (ISM) and supersonic turbulence preferentially located in the Galactic plane. Correspondingly, we consider the Galactic distribution of electron density fluctuations consisting of not only a Kolmogorov density spectrum but also a short-wave-dominated density spectrum with the density structure formed at small scales due to shocks. The resulting dependence of the scatter broadening time on the dispersion measure (DM) naturally interprets the existing observational data for both low and high-DM pulsars. According to the criteria that we derive for a quantitative determination of scattering regimes over wide ranges of DMs and frequencies $\nu$, we find that the pulsars with low DMs are primarily scattered by the Kolmogorov turbulence, while those at low Galactic latitudes with high DMs undergo more enhanced scattering dominated by the supersonic turbulence, where the corresponding density spectrum has a spectral index $\approx 2.6$. Besides, by considering a volume filling factor of the density structures with the dependence on $\nu$ as $\propto {\nu }^{1.4}$ in the supersonic turbulence, our model can also explain the observed shallower $\nu$ scaling of the scattering time than the Kolmogorov scaling for the pulsars with relatively large DMs. The comparison between our analytical results and the scattering measurements of pulsars in turn makes a useful probe of the properties of the large-scale ISM turbulence, e.g., an injection scale of $\sim 100$ pc, and also characteristics of small-scale density structures.

11 pages, 3 figures, accepted for publication in ApJ

References in corpus (15)

• Theory of Star Formation
• The Statistics of Supersonic Isothermal Turbulence
• Density Fluctuations in MHD Turbulence: Spectra, Intermittency and Topology
• The outer scale of turbulence in the magneto-ionized Galactic interstellar medium
• Numerical simulations of compressively driven interstellar turbulence: I. Isothermal gas
• The Turbulent Warm Ionized Medium: Emission Measure Distribution and MHD Simulations
• Velocity centroids as tracers of the turbulent velocity statistics
• The Power Spectrum of Supersonic Turbulence in Perseus
• Scaling Relations of Compressible MHD Turbulence
• Turbulence in the Interstellar Medium
• Measuring the Alfvenic Nature of the Interstellar Medium: Velocity Anisotropy Revisited
• The analysis of the largest sample of multi-frequency pulsar scatter time estimates
• On the origin of the scatter broadening of fast radio burst pulses and astrophysical implications
• Probing Nearby CR Accelerators and ISM Turbulence with Milagro Hot Spots
• Densities and filling factors of the DIG in the Solar neighbourhood

Cited by in corpus (14)

• The Physics of Fast Radio Bursts
• Temporal Scattering, Depolarization, and Persistent Radio Emission from Magnetized Inhomogeneous Environments Near Repeating Fast Radio Burst Sources
• Magnetic field amplification in supernova remnants
• Turbulence in a self-gravitating molecular cloud core
• The Velocity Statistics of Turbulent Clouds in the Presence of Gravity, Magnetic fields, Radiation, and Outflow Feedback
• Flux density variability of 286 radio pulsars from a decade of monitoring
• Scattering study of Pulsars below 100 MHz using LWA1
• Measuring magnetization with rotation measures and velocity centroids in supersonic MHD turbulence
• Nonuniversal interstellar density spectra probed by pulsars
• Probing the intergalactic turbulence with fast radio bursts
• Probing pulsar scattering between 120 and 280 MHz with the MWA
• Projected velocity statistics of interstellar turbulence
• Quasi-perpendicular shock acceleration and TDE radio flares
• Diffusion of cosmic rays in MHD turbulence