Wavelet Analysis of Differential TEC Measurements Obtained Using LOFAR

Radio Science, vol. 59

Abstract

Abstract Radio interferometers used to make astronomical observations, such as the LOw Frequency ARray (LOFAR), experience distortions imposed upon the received signal due to the ionosphere as well as those from instrumental errors. Calibration using a well‐characterized radio source can be used to mitigate these effects and produce more accurate images of astronomical sources, and the calibration process provides measurements of ionospheric conditions over a wide range of length scales. The basic ionospheric measurement this provides is differential Total Electron Content (TEC, the integral of electron density along the line of sight). Differential TEC measurements made using LOFAR have a precision of <1 mTECu and therefore enable investigation of ionospheric disturbances which may be undetectable to many other methods. We demonstrate an approach to identify ionospheric waves from these data using a wavelet transform and a simple plane wave model. The noise spectra are robustly characterized to provide uncertainty estimates for the fitted parameters. An example is shown in which this method identifies a wave with an amplitude an order of magnitude below those reported using Global Navigation Systems Satellite TEC measurements. Artificially generated data are used to test the accuracy of the method and establish the range of wavelengths which can be detected using this method with LOFAR data. This technique will enable the use of a large and mostly unexplored data set to study traveling ionospheric disturbances over Europe.

Authors 8

1. Ben Boyde

   University of Birmingham

   Affiliation as printed

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK

2. Alan George Wood corresponding

   University of Birmingham

   Affiliation as printed

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK

3. Gareth D. Dorrian

   University of Birmingham

   Affiliation as printed

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK

4. Frits Sweijen Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University RA Leiden The Netherlands

   Leiden Observatory, Leiden University RA Leiden The Netherlands

5. F. de Gasperin

   Universität Hamburg · Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

   Affiliation as printed

   Hamburger Sternwarte, University of Hamburg Hamburg Germany

   INAF ‐ Istituto di Radioastronomia Bologna Italy

   Hamburger Sternwarte, University of Hamburg Hamburg Germany

   INAF - Istituto di Radioastronomia Bologna Italy

6. M. Mevius

   Netherlands Institute for Radio Astronomy

   Affiliation as printed

   ASTRON – The Netherlands Institute for Radio Astronomy PD Dwingeloo The Netherlands

7. Kasia Beser

   Netherlands Institute for Radio Astronomy

   Affiliation as printed

   ASTRON – The Netherlands Institute for Radio Astronomy PD Dwingeloo The Netherlands

8. David R. Themens

   University of Birmingham

   Affiliation as printed

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK

   Space Environment and Radio Engineering, School of Engineering, University of Birmingham Birmingham UK