The outer scale of turbulence in the magneto-ionized Galactic interstellar medium

Abstract

We analyze Faraday rotation and depolarization of extragalactic radio point sources in the direction of the inner Galactic plane to determine the outer scale and amplitude of the rotation measure power spectrum. Structure functions of rotation measure show lower amplitudes than expected when extrapolating electron density fluctuations to large scales assuming a Kolmogorov spectral index. This implies an outer scale of those fluctuations on the order of a parsec, much smaller than commonly assumed. Analysis of partial depolarization of point sources independently indicates a small outer scale of a Kolmogorov power spectrum. In the Galaxy's spiral arms, no rotation measure fluctuations on scales above a few parsecs are measured. In the interarm regions fluctuations on larger scales than in spiral arms are present, and show power law behavior with a shallow spectrum. These results suggest that in the spiral arms stellar sources such as stellar winds or protostellar outflows dominate the energy injection for the turbulent energy cascade on parsec scales, while in the interarm regions supernova and super bubble explosions are the main sources of energy on scales on the order of 100 parsecs.

14 pages, 6 figures, accepted by ApJ

References in corpus (5)

• Rotation Measures of Extragalactic Sources Behind the Southern Galactic Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky Way
• The Southern Galactic Plane Survey: Polarized Radio Continuum Observations and Analysis
• The spatial energy spectrum of magnetic fields in our Galaxy
• An improved solar wind electron-density model for pulsar timing
• Polarization shadows of extragalactic sources by the local magneto-ionic ISM

Cited by in corpus (24)

• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• The Turbulent Warm Ionized Medium: Emission Measure Distribution and MHD Simulations
• Simulating polarized Galactic synchrotron emission at all frequencies, the Hammurabi code
• Detection of microgauss coherent magnetic fields in a galaxy five billion years ago
• Magnetic Fields in the Milky Way
• Fast simulations for intensity mapping experiments
• Scatter broadening of pulsars and implications on the interstellar medium turbulence
• Galactic interstellar turbulence in the southern sky seen through spatial gradients of the polarization vector
• Probing Nearby CR Accelerators and ISM Turbulence with Milagro Hot Spots
• On the origin of the scatter broadening of fast radio burst pulses and astrophysical implications
• Constraints from Faraday rotation on the magnetic field structure in the Galactic halo
• Three-dimensional extinction mapping using Gaussian random fields
• Cosmic Magnetism in Centimeter and Meter Wavelength Radio Astronomy
• Properties of the Magneto-ionic Medium in the Halo of M51 revealed by Wide-band Polarimetry
• Statistical Techniques for Detecting the Intergalactic Magnetic Field from Large Samples of Extragalactic Faraday Rotation Data
• Detection of a ~20 kpc coherent magnetic field in the outskirt of merging spirals: the Antennae galaxies
• Exploring the Intergalactic Magnetic Field by Means of Faraday Tomography
• Large-Scale Cosmic-Ray Anisotropy as a Probe of Interstellar Turbulence
• Using Red Clump Stars to Decompose the Galactic Magnetic Field with Distance
• Halpha and [S II] emission from warm ionized gas in the Scutum-Centaurus Arm
• Scatter broadening of compact radio sources by the ionized intergalactic medium: Prospects for detection with Space VLBI and the SKA
• Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey
• Probing magnetic fields with Square Kilometre array and its precursors
• Galactic turbulence and paleoclimate variability