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

摘要

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