Probing the Solar Corona and the Solar Wind Using Angular Broadening Observations with the SKA

TL;DR

This paper discusses how the Square Kilometre Array can significantly enhance the study of the solar corona and solar wind through angular broadening observations of compact radio sources, revealing turbulence and magnetic field structures.

Contribution

It introduces the potential of SKA to vastly improve angular broadening measurements, enabling detailed probing of coronal turbulence and magnetic fields beyond current limitations.

Findings

Enhanced sensitivity and resolution will increase observable sources.

Potential to study turbulence amplitude and dissipation scales.

Improved understanding of solar-wind heating and magnetic field orientation.

Abstract

Angular broadening observations of compact radio sources provide a powerful method for probing the solar corona and solar wind. Such observations enable studies of the phase structure function, turbulence amplitude, intermediate-scale density fluctuations, solar-wind heating rates, and dissipation scales. When a compact radio source is observed through coronal or solar-wind plasma, several observable effects can arise: (1) the apparent source size increases because of scattering by turbulent plasma, producing angular broadening; (2) the source flux density decreases because of scattering and absorption; (3) the observed angular broadening can be anisotropic, reflecting anisotropic turbulence in the corona and solar wind; and (4) the position angle of the anisotropy, measured from north through east, can help infer the orientation of the coronal magnetic field. These effects provide insights into the physical processes governing the solar wind and its interaction with electromagnetic waves, and they offer constraints on coronal turbulence and magnetic-field structure. At present, angular broadening studies remain limited and have mostly focused on very bright radio sources such as Tau A. The unprecedented sensitivity and angular resolution of the Square Kilometre Array are expected to greatly expand the number of suitable background sources, opening a new window on the solar corona, solar wind, and heliosphere.