High-precision Measurements of Ionospheric TEC Gradients with the Very Large Array VHF System

TL;DR

This paper demonstrates that the Very Large Array (VLA) can measure ionospheric TEC gradients with high precision using bright cosmic radio sources, enabling detailed studies of ionospheric fluctuations across various scales.

Contribution

The paper introduces a method to achieve 0.0003 TECU precision in differential TEC measurements using the VLA, expanding capabilities for ionospheric research.

Findings

VLA can measure delta-TEC with 0.0003 TECU precision.

Techniques for computing TEC gradients and small-scale fluctuations are demonstrated.

High-precision measurements enable detailed ionospheric fluctuation analysis.

Abstract

We have used a relatively long, contiguous VHF observation of a bright cosmic radio source (Cygnus A) with the Very Large Array (VLA) to demonstrate the capability of this instrument to study the ionosphere. This interferometer, and others like it, can observe ionospheric total electron content (TEC) fluctuations on a much wider range of scales than is possible with many other instruments. We have shown that with a bright source, the VLA can measure differential TEC values between pairs of antennas (delta-TEC) with an precision of 0.0003 TECU. Here, we detail the data reduction and processing techniques used to achieve this level of precision. In addition, we demonstrate techniques for exploiting these high-precision delta-TEC measurements to compute the TEC gradient observed by the array as well as small-scale fluctuations within the TEC gradient surface. A companion paper details specialized spectral analysis techniques used to characterize the properties of wave-like fluctuations within this data.