Wavelet Analysis of Differential TEC Measurements Obtained Using LOFAR

Ben Boyde; Alan Wood; Gareth Dorrian; Frits Sweijen; Francesco de Gasperin; Maaijke Mevius; Kasia Beser; David Themens

doi:10.1029/2023rs007871

Wavelet Analysis of Differential TEC Measurements Obtained Using LOFAR

Ben Boyde, Alan Wood^*, Gareth Dorrian, Frits Sweijen, Francesco de Gasperin, Maaijke Mevius, Kasia Beser, David Themens

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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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.

Original language	English
Article number	e2023RS007871
Number of pages	19
Journal	Radio Science
Volume	59
Issue number	4
Early online date	30 Mar 2024
DOIs	https://doi.org/10.1029/2023rs007871
Publication status	Published - Apr 2024

Bibliographical note

Acknowledgments:
This work is supported by the Leverhulme Trust under Research Project Grant RPG-2020-140. Ben Boyde acknowledges receipt of a PhD studentship from the same grant. This paper is based on data obtained with the International LOFAR Telescope (ILT). LOFAR (van Haarlem et al., 2013) is the LOw Frequency ARray designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d’Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland. LOFAR data are available at https://lta.lofar.eu/.

Keywords

mid‐latitude
LOFAR
ionosphere
MSTID

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10.1029/2023rs007871Licence: Creative Commons: Attribution (CC BY)

BoydeB2024WaveletFinal published version, 2.03 MBLicence: Creative Commons: Attribution (CC BY)

A world of complexity: The ionosphere seen as never before
Wood, A.
Leverhulme Trust
1/02/21 → 31/01/25
Project: Research

Cite this

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title = "Wavelet Analysis of Differential TEC Measurements Obtained Using LOFAR",

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.",

keywords = "mid‐latitude, LOFAR, ionosphere, MSTID",

author = "Ben Boyde and Alan Wood and Gareth Dorrian and Frits Sweijen and {de Gasperin}, Francesco and Maaijke Mevius and Kasia Beser and David Themens",

note = "Acknowledgments: This work is supported by the Leverhulme Trust under Research Project Grant RPG-2020-140. Ben Boyde acknowledges receipt of a PhD studentship from the same grant. This paper is based on data obtained with the International LOFAR Telescope (ILT). LOFAR (van Haarlem et al., 2013) is the LOw Frequency ARray designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Universit{\'e} d{\textquoteright}Orl{\'e}ans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland. LOFAR data are available at https://lta.lofar.eu/.",

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volume = "59",

journal = "Radio Science",

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publisher = "American Geophysical Union",

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AU - Boyde, Ben

AU - Wood, Alan

AU - Dorrian, Gareth

AU - Sweijen, Frits

AU - de Gasperin, Francesco

AU - Mevius, Maaijke

AU - Beser, Kasia

AU - Themens, David

N1 - Acknowledgments: This work is supported by the Leverhulme Trust under Research Project Grant RPG-2020-140. Ben Boyde acknowledges receipt of a PhD studentship from the same grant. This paper is based on data obtained with the International LOFAR Telescope (ILT). LOFAR (van Haarlem et al., 2013) is the LOw Frequency ARray designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d’Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland. LOFAR data are available at https://lta.lofar.eu/.

PY - 2024/4

Y1 - 2024/4

N2 - 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.

AB - 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.

KW - mid‐latitude

KW - LOFAR

KW - ionosphere

KW - MSTID

U2 - 10.1029/2023rs007871

DO - 10.1029/2023rs007871

M3 - Article

SN - 0048-6604

VL - 59

JO - Radio Science

JF - Radio Science

IS - 4

M1 - e2023RS007871

ER -

Wavelet Analysis of Differential TEC Measurements Obtained Using LOFAR

Abstract

Bibliographical note

Keywords

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A world of complexity: The ionosphere seen as never before

Cite this