Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

TL;DR

This study analyzes ionospheric fluctuations using the Murchison Widefield Array's radio observations, revealing complex plasma structures and waves at regional scales, including traveling disturbances and magnetic field-aligned bands.

Contribution

First power spectrum analysis of ionospheric fluctuations using MWA data, demonstrating its capability to probe plasma structures at regional scales.

Findings

Detection of traveling ionospheric disturbances (TIDs)

Observation of narrow, slowly-drifting bands aligned with Earth's magnetic field

Complex structures and waves in ionospheric plasma

Abstract

Low-frequency, wide field-of-view (FoV) radio telescopes such as the Murchison Widefield Array (MWA) enable the ionosphere to be sampled at high spatial completeness. We present the results of the first power spectrum analysis of ionospheric fluctuations in MWA data, where we examined the position offsets of radio sources appearing in two datasets. The refractive shifts in the positions of celestial sources are proportional to spatial gradients in the electron column density transverse to the line of sight. These can be used to probe plasma structures and waves in the ionosphere. The regional (10-100 km) scales probed by the MWA, determined by the size of its FoV and the spatial density of radio sources (typically thousands in a single FoV), complement the global (100-1000 km) scales of GPS studies and local (0.01-1 km) scales of radar scattering measurements. Our data exhibit a range of complex structures and waves. Some fluctuations have the characteristics of travelling ionospheric disturbances (TIDs), while others take the form of narrow, slowly-drifting bands aligned along the Earth's magnetic field.