Tracing the Heliospheric Magnetic Field via Anisotropic Radio-Wave Scattering

Abstract

Astrophysical radio sources are embedded in turbulent magnetised environments. In the 1 MHz sky, solar radio bursts are the brightest sources, produced by electrons travelling along magnetic field lines from the Sun through the heliosphere. We demonstrate that the magnetic field not only guides the emitting electrons, but also directs radio waves via anisotropic scattering from density irregularities in the magnetised plasma. Using multi-vantage-point type III solar radio burst observations and anisotropic radio wave propagation simulations, we show that the interplanetary field structure is encoded in the observed radio emission directivity, and that large-scale turbulent channelling of radio waves is present over large distances, even for relatively weak anisotropy in the embedded density fluctuations. Tracing the radio emission at many frequencies (distances), the effects of anisotropic scattering can be disentangled from the electron motion along the interplanetary magnetic field, and the emission source locations are unveiled. Our analysis suggests that magnetic field structures within turbulent media could be reconstructed using radio observations and is found consistent with the Parker field, offering a novel method for remotely diagnosing the large-scale field structure in the heliosphere and other astrophysical plasmas.

14 pages, 9 figures. Accepted in Scientific Reports

References in corpus (11)

• The Solar Orbiter mission -- Science overview
• Fast Radio Bursts
• The Solar Orbiter Science Activity Plan: translating solar and heliospheric physics questions into action
• An Anisotropic Density Turbulence Model from the Sun to 1 au Derived From Radio Observations
• Fine structure of type III solar radio bursts from Langmuir wave motion in turbulent plasma
• Bimodal distribution of the solar wind at 1 AU
• Simulations of radio-wave anisotropic scattering to interpret type III radio bursts measurements by Solar Orbiter, Parker Solar Probe, STEREO and Wind
• Sub-second time evolution of Type III solar radio burst sources at fundamental and harmonic frequencies
• Solar Orbiter/RPW antenna calibration in the radio domain and its application to type III burst observations
• Bridging High-Density, Electron Beam Coronal Transport and Deep Chromospheric Heating in Stellar Flares
• Magnetic Field Geometry and Anisotropic Scattering Effects on Solar Radio Burst Observations