Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)

<p>In order to provide a scientific base to the NeQuick characterisation under disturbed conditions, the comparison of its performance for quiet and storm days is investigated in the southern mid-latitude. This investigation was realised using the two versions of the NeQuick model which wer...

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Main Authors:	S. M. Ahoua, J. B. Habarulema, O. K. Obrou, P. J. Cilliers, Z. K. Zaka
Format:	Article
Language:	English
Published:	Copernicus Publications 2018-09-01
Series:	Annales Geophysicae
Online Access:	https://www.ann-geophys.net/36/1161/2018/angeo-36-1161-2018.pdf

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record_format	Article
spelling	doaj-2c14ad262f2f45a3aaaa2e5e5240f0952020-11-24T22:53:29ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762018-09-01361161117010.5194/angeo-36-1161-2018Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)S. M. Ahoua0S. M. Ahoua1J. B. Habarulema2J. B. Habarulema3O. K. Obrou4P. J. Cilliers5P. J. Cilliers6Z. K. Zaka7South African National Space Agency (SANSA) Space Science Directorate, P.O. Box 32 Hermanus, 7200, South AfricaLaboratoire de Physique de L'Atmosphère, Université F.H.B. de Cocody, 22 BP 582 Abidjan 22, Côte d'IvoireSouth African National Space Agency (SANSA) Space Science Directorate, P.O. Box 32 Hermanus, 7200, South AfricaDepartment of Physics and Electronics, Rhodes University, Grahamstown, 6140, South AfricaLaboratoire de Physique de L'Atmosphère, Université F.H.B. de Cocody, 22 BP 582 Abidjan 22, Côte d'IvoireSouth African National Space Agency (SANSA) Space Science Directorate, P.O. Box 32 Hermanus, 7200, South AfricaDepartment of Electrical Engineering, University of Cape Town, Cape Town, South AfricaLaboratoire de Physique de L'Atmosphère, Université F.H.B. de Cocody, 22 BP 582 Abidjan 22, Côte d'Ivoire<p>In order to provide a scientific base to the NeQuick characterisation under disturbed conditions, the comparison of its performance for quiet and storm days is investigated in the southern mid-latitude. This investigation was realised using the two versions of the NeQuick model which were adapted to local and storm-specific response by using the critical frequency of the F2 layer (<i>fo</i>F2) and the propagation factor (<i>M</i>(3000)F2) derived from three South African ionosonde measurements, Hermanus (34.40° S, 19.20° E), Grahamstown (33.30° S, 26.50° E) and Louisvale (28.50° S, 21.20° E). The number of free electrons contained within a 1 m squared column section known as total electron content (TEC) is a widely used ionospheric parameter to estimate its impact on the radio signal passing through. In this study, the TEC derived from the adapted NeQuick version is compared with observed TEC derived from Global Navigation Satellite System (GNSS) data from co-located or nearby GNSS dual-frequency receivers. The Hermanus <i>K</i>-index is used to select all the disturbed days (<i>K</i>-index  ≥  5) upon moving from low to high solar activity (from 2009 to 2012). For each disturbed day, a quiet reference day of the same month was chosen for the investigation. The study reveals that the NeQuick model shows similar reliability for both magnetic quiet and disturbed conditions, but its accuracy is affected by the solar activity. The model is much better for moderate solar activity epochs (2009 and 2010), while it exhibits a discrepancy with observations during high solar activity epochs. For instance in Hermanus, the difference between GPS TEC and NeQuick TEC (ΔTEC) is generally lower than 10 TECu in 2009, and it sometimes reaches 20 TECu in 2011 and 2012. It is also noticed that NeQuick 2 is more accurate than NeQuick 1, with an improvement in TEC estimation more significant for the high solar activity epochs. The improvement realised in the latest version of NeQuick is more than 15 % and sometimes reaches 50 %.</p>https://www.ann-geophys.net/36/1161/2018/angeo-36-1161-2018.pdf
collection	DOAJ
language	English
format	Article
sources	DOAJ
author	S. M. Ahoua S. M. Ahoua J. B. Habarulema J. B. Habarulema O. K. Obrou P. J. Cilliers P. J. Cilliers Z. K. Zaka
spellingShingle	S. M. Ahoua S. M. Ahoua J. B. Habarulema J. B. Habarulema O. K. Obrou P. J. Cilliers P. J. Cilliers Z. K. Zaka Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012) Annales Geophysicae
author_facet	S. M. Ahoua S. M. Ahoua J. B. Habarulema J. B. Habarulema O. K. Obrou P. J. Cilliers P. J. Cilliers Z. K. Zaka
author_sort	S. M. Ahoua
title	Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)
title_short	Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)
title_full	Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)
title_fullStr	Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)
title_full_unstemmed	Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)
title_sort	evaluation of the nequick model performance under different geomagnetic conditions over south africa during the ascending phase of the solar cycle (2009–2012)
publisher	Copernicus Publications
series	Annales Geophysicae
issn	0992-7689 1432-0576
publishDate	2018-09-01
description	<p>In order to provide a scientific base to the NeQuick characterisation under disturbed conditions, the comparison of its performance for quiet and storm days is investigated in the southern mid-latitude. This investigation was realised using the two versions of the NeQuick model which were adapted to local and storm-specific response by using the critical frequency of the F2 layer (<i>fo</i>F2) and the propagation factor (<i>M</i>(3000)F2) derived from three South African ionosonde measurements, Hermanus (34.40° S, 19.20° E), Grahamstown (33.30° S, 26.50° E) and Louisvale (28.50° S, 21.20° E). The number of free electrons contained within a 1 m squared column section known as total electron content (TEC) is a widely used ionospheric parameter to estimate its impact on the radio signal passing through. In this study, the TEC derived from the adapted NeQuick version is compared with observed TEC derived from Global Navigation Satellite System (GNSS) data from co-located or nearby GNSS dual-frequency receivers. The Hermanus <i>K</i>-index is used to select all the disturbed days (<i>K</i>-index  ≥  5) upon moving from low to high solar activity (from 2009 to 2012). For each disturbed day, a quiet reference day of the same month was chosen for the investigation. The study reveals that the NeQuick model shows similar reliability for both magnetic quiet and disturbed conditions, but its accuracy is affected by the solar activity. The model is much better for moderate solar activity epochs (2009 and 2010), while it exhibits a discrepancy with observations during high solar activity epochs. For instance in Hermanus, the difference between GPS TEC and NeQuick TEC (ΔTEC) is generally lower than 10 TECu in 2009, and it sometimes reaches 20 TECu in 2011 and 2012. It is also noticed that NeQuick 2 is more accurate than NeQuick 1, with an improvement in TEC estimation more significant for the high solar activity epochs. The improvement realised in the latest version of NeQuick is more than 15 % and sometimes reaches 50 %.</p>
url	https://www.ann-geophys.net/36/1161/2018/angeo-36-1161-2018.pdf
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Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)

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