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Comparison of Ionospheric Anomalies Over African Equatorial/Low Comparison of Ionospheric Anomalies over African Equatorial/Low-latitude Region with IRI-2016 Model Predictions during the Maximum Phase of Solar Cycle 24 Paul Amaechi, Elijah Oyeyemi, Andrew Akala, Mohamed Kaab, Waqar Younas, Zouhair Benkhaldoun, Majid Khan, Christine Mazaudier To cite this version: Paul Amaechi, Elijah Oyeyemi, Andrew Akala, Mohamed Kaab, Waqar Younas, et al.. Comparison of Ionospheric Anomalies over African Equatorial/Low-latitude Region with IRI-2016 Model Predic- tions during the Maximum Phase of Solar Cycle 24. Advances in Space Research, Elsevier, 2021, 10.1016/j.asr.2021.03.040. hal-03213004 HAL Id: hal-03213004 https://hal.archives-ouvertes.fr/hal-03213004 Submitted on 30 Apr 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Advances in Sp ace Research Comparison of Ionospheric Anomalies over African Equatorial/Low-latitude Region with IRI-2016 Model Predictions during the Maximum Phase of Solar Cycle 24 --Manuscript Draft-- Manuscript Number: AISR-D-21-00077R1 Article Type: EM -Earth Magnetosphere/Upper Atmosphere Keywords: IRI-2016, Equatorial Ionization Anomaly, Hemispheric asymmetry, Winter anomaly, Semiannual anomaly Corresponding Author: Paul Obiakara Amaechi, Ph.D Chrisland University Lagos, NIGERIA First Author: Paul Obiakara Amaechi, Ph.D Order of Authors: Paul Obiakara Amaechi, Ph.D Elijah O. Oyeyemi, Ph.D Andrew Akala, Ph.D Mohamed Kaab, Ph.D Waqar Younas, MSc Zouhair Benkhaldoun, Ph.D Majid Khan, Ph.D Christine Amory Mazaudier, Ph.D Abstract: The capability of IRI-2016 in reproducing the hemispheric asymmetry, the winter and semiannual anomalies has been assessed over the equatorial ionization anomaly (EIA) during quiet periods of years 2013-2014. The EIA reconstructed using Total Electron Content (TEC) derived from Global Navigation Satellite System was compared with that computed using IRI-2016 along longitude 25o - 40oE. These were analyzed along with hemispheric changes in the neutral wind derived from the horizontal wind model and the TIMED GUVI columnar O/N2 data. IRI-2016 clearly captured the hemispheric asymmetry of the anomaly during all seasons albeit with some discrepancies in the magnitude and location of the crests. The winter anomaly in TEC which corresponded with greater O/N2 in the winter hemisphere was also predicted by IRI-2016 during December solstice. The model also captured the semiannual anomaly with stronger crests in the northern hemisphere. Furthermore, IRI-2016 reproduced the variation trend of the asymmetry index (A) in December solstice and equinox during noon. However, in June solstice the model failed to capture the winter anomaly and misrepresented the variation of A. This was linked with its inability to accurately predict the pattern of the neutral wind, the maximum height of the F2 layer and the changes in O/N2 in both hemispheres. The difference between variations of EUV and F10.7 fluxes was also a potential source of errors in IRI-2016. The results highlight the significance of the inclusion of wind data in IRI-2016 in order to enhance its performance over East Africa. Response to Reviewers: Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Highlights Highlights 1. IRI-2016 captured the hemispheric asymmetry over the African EIA with discrepancies in crests’ magnitude/ location 2. The winter anomaly with greater O/N2 in the winter hemisphere was predicted by IRI-2016 during December solstice only 3. The semiannual anomaly was predicted with stronger northern crests while the asymmetry was missed in June solstice Manuscript Click here to view linked References 1 2 3 4 Comparison of Ionospheric Anomalies over African Equatorial/Low-latitude Region 5 with IRI-2016 Model Predictions during the Maximum Phase of Solar Cycle 24 6 7 *Paul O. Amaechi1, Elijah O. Oyeyemi2, Andrew O. Akala2,3, Mohamed Kaab4,5, Waqar 8 6 4 6 7,8 9 Younas , Zouhair Benkhaldoun , Majid Khan , Christine-Amory Mazaudier 10 11 1Department of Physical Sciences, Chrisland University, Abeokuta, Nigeria 12 2Department of Physics, University of Lagos, Akoka, Yaba, Lagos, Nigeria 13 3Maritime Institute, University of Lagos, Akoka, Yaba, Lagos, Nigeria 14 4 15 Oukaimeden Observatory, LPHEA, FSSM, Cadi Ayyad University, Marrakech, 16 Morrocco 17 5National School of Applied Sciences of Beni Mellal, Sultan Moulay Sliman University, 18 Beni Mellal, Morocco 19 6 20 Department of Physics, Quaid-i-Azam University, Islamabad 45320, Pakistan 7 21 LPP, CNRS/Ecole Polytechnique/Sorbonne Université/Université Paris- 22 Sud/Observatoire de Paris, 75006 Paris, France 23 8 T/ICT4D Abdus Salam ICTP, Italy 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 *Corresponding author: Paul O. Amaechi (email: [email protected]) 56 57 Tel: +2348032050324 58 59 60 61 62 1 63 64 65 1 2 3 4 Abstract 5 6 7 The capability of IRI-2016 in reproducing the hemispheric asymmetry, the winter and 8 semiannual anomalies has been assessed over the equatorial ionization anomaly (EIA) 9 10 during quiet periods of years 2013-2014. The EIA reconstructed using Total Electron 11 Content (TEC) derived from Global Navigation Satellite System was compared with that 12 computed using IRI-2016 along longitude 25o - 40oE. These were analyzed along with 13 14 hemispheric changes in the neutral wind derived from the horizontal wind model and the 15 TIMED GUVI columnar O/N2 data. IRI-2016 clearly captured the hemispheric 16 17 asymmetry of the anomaly during all seasons albeit with some discrepancies in the 18 magnitude and location of the crests. The winter anomaly in TEC which corresponded 19 with greater O/N in the winter hemisphere was also predicted by IRI-2016 during 20 2 21 December solstice. The model also captured the semiannual anomaly with stronger crests 22 in the northern hemisphere. Furthermore, IRI-2016 reproduced the variation trend of the 23 24 asymmetry index (A) in December solstice and equinox during noon. However, in June 25 solstice the model failed to capture the winter anomaly and misrepresented the variation 26 of A. This was linked with its inability to accurately predict the pattern of the neutral 27 28 wind, the maximum height of the F2 layer and the changes in O/N2 in both hemispheres. 29 The difference between variations of EUV and F10.7 fluxes was also a potential source 30 31 of errors in IRI-2016. The results highlight the significance of the inclusion of wind data 32 in IRI-2016 in order to enhance its performance over East Africa. 33 34 35 Keywords: IRI-2016, Equatorial Ionization Anomaly, Hemispheric asymmetry, Winter 36 37 anomaly, Semiannual anomaly. 38 39 40 41 1. Introduction 42 43 The ionosphere is the ionized part of the atmosphere which extends from about 60 44 45 to 1000 km (Hargreaves, 1995) and comprises of free ions and electrons in sufficient 46 47 number as to affecting radio signals. Ionospheric anomalies which were first reported in 48 the works of earlier scientists (Appleton, 1938; Berkner et al., 1936) have been the 49 50 subject of various investigations over the years. Ionospheric anomaly originally referred 51 52 to departures from the solar controlled behavior in which the critical frequency foF2 53 54 varies regularly with the solar zenith angle ( ) as it does in the well-known Chapman 55 56 layer (Rishbeth, 1998). According to Rishbeth휒 (1998) the term anomaly originally meant 57 58 ‘‘any departure from solar controlled behavior in which the critical frequency foF2 varies 59 regularly with the solar zenith angle ( ) as it does in the well-known Chapman layer 60 ’’. 61 휒 62 2 63 64 65 1 2 3 4 Salient ionospheric anomalies are the seasonal anomaly otherwise known as the winter 5 6 anomaly, the annual anomaly or non-seasonal anomaly and the semiannual anomaly as 7 8 well as the equatorial ionization anomaly (EIA). 9 10 The winter anomaly is characterized by greater peak electron density of the F2 11 12 layer (NmF2) in the winter hemisphere than its conjugate summer hemisphere during 13 14 solstices (Torr and Torr, 1973). For the annual anomaly, the NmF2 is significantly greater 15 16 in December than June solstice globally (Gowtam and Tulasi Ram, 2017) while for the 17 18 semiannual anomaly it is higher in equinox than solstice (Rishbeth, 1998; Yasyukevich et 19 20 al., 2018). The EIA also known as the Appleton Anomaly (Appleton, 1946), is an 21 essentially feature of the low-latitude ionosphere. It is discernable by the reduction in 22 23 ionization at the magnetic equator (the trough) as against two peaks on both sides of it at 24 25 about ±15o magnetic latitude (the crests) (Namba and Maeda, 1939). 26 27 28 Several mechanisms have been put forth to explain the ionospheric anomalies. It 29 30 has been suggested that the winter anomaly is caused by change in neutral composition, 31 32 driven by global thermospheric circulation, which is greater in winter than in summer 33 (Burns et al., 2014; Rishbeth and Setty, 1961; Zou et al., 2000). The annual anomaly is 34 35 driven by the higher December solstice solar flux which is responsible for greater 36 37 dissociation of molecular oxygen than June solstice (Yonezawa and Arima, 1959) as well 38 39 as by changes in the Sun-Earth distance, difference between the geographic and magnetic 40 41 equator and the tilt of the geomagnetic dipole (Zeng et al., 2008).
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