This study aims at
discussing longitudinal effects on the variability of the vertical E × B drift velocity at low latitudes, specifically over African sector. To this
effect, observations from ground-based magnetometers and the Ion Velocity Meter
experiment onboard C/NOFS satellite are analyzed in conjunction with equatorial electric field and neutral
wind model estimates under geomagnetically quiet conditions in the years 2012-2013. Notwithstanding the
limitation in data over Africa, the combination of ground-based and in-situ observations confirmed the existence of longitudinal differences in the E × B between the
Atlantic, Western and Eastern African sectors. This was well reproduced by the
equatorial electric field model (EEFM) which showed that during noon, the peak
of the equatorial electric field (EEF) was the lowest in the Atlantic sector,
with an increasing trend towards the Eastern longitude. The Horizontal Wind
Model 14 (HWM14) showed that the eastward zonal (poleward meridional) wind
velocity was the lowest (highest) in the Eastern sector. Furthermore, the zonal
(meridional) wind increased (decreased) from the Eastern to the Atlantic
sector. These results highlight the contribution of the neutral wind velocity
in driving the longitudinal difference in the vertical drift velocity over
Africa.
References
[1]
Araujo-Pradere, E.A., Anderson, D.N. and Fedrizzi, M. (2011) Communications/Navigation Outage Forecasting System Observational Support for the Equatorial E × B Drift Velocities Associated with the Four-Cell Tidal Structures. Radio Science, 46, RS0D09. https://doi.org/10.1029/2010RS004557
[2]
Hanson, W.B. and Moffett, R.J. (1966) Ionization Transport Effects in the Equatorial F Region. Journal of Geophysical Research, 71, 5559-5572. https://doi.org/10.1029/JZ071i023p05559
[3]
Khadka, S.M., Valladares, C.E., Sheehan, R. and Gerrard, A.J. (2018) Effects of Electric Field and Neutral Wind on the Asymmetry of Equatorial Ionization Anomaly. Radio Science, 53, 683-697. https://doi.org/10.1029/2017RS006428
[4]
Subhadra Devi, P.K. (2013) Behaviour of Ionosphere and Its Interaction with Solar Magnetosphere System. PhD Thesis, School of Pure and Applied Physics, Mahatma Gandhi University, Ri Bhoi.
[5]
Sultan, P.J. (1996) Linear Theory and Modeling of the Rayleigh-Taylor Instability Leading to the Occurrence of Equatorial Spread F. Journal of Geophysical Research, 101, 26875-26891. https://doi.org/10.1029/96JA00682
Amaechi, P.O., Oyeyemi, E.O., Akala, A.O., Messanga, H.E., Panda, S.K., Seemala, G.K., et al. (2021) Ground Based GNSS and C/NOFS Observations of Ionospheric Irregularities over Africa: A Case Study of the 2013 St. Patrick’s Day Geomagnetic Storm. Space Weather, 19, e2020SW002631. https://doi.org/10.1029/2020SW002631
[8]
Yizengaw, E. and Moldwin, M.B. (2009) African Meridian B-Field Education and Research (AMBER) Array. Earth, Moon, and Planets, 104, 237-246. https://doi.org/10.1007/s11038-008-9287-2
[9]
Rastogi, R.G. and Klobuchar, J.A. (1990) Ionospheric Electron Content within the Equatorial F2 Layer Anomaly Belt. Journal of Geophysical Research, 95, 19,045-19,052. https://doi.org/10.1029/JA095iA11p19045
[10]
Gonzales, C.A., Kelley, M.C., Fejer, B.G., Vickrey, J.F. and Woodman, R.F. (1979) Equatorial Electric Fields during Magnetically Disturbed Conditions. 2: Implications of Simultaneous Auroral and Equatorial Measurements. Journal of Geophysical Research: Space Physics, 84, 5803-5812. https://doi.org/10.1029/JA084iA10p05803
[11]
Kassamba, A.A., Doumbia, V., Obrou, O.K., et al. (2020) Estimating the Daytime Vertical E × B Drift Velocities in F-Region of the Equatorial Ionosphere Using the IEEY and AMBER Magnetic Data in West Africa. Advances in Space Research, 65, 2573-2585. https://doi.org/10.1016/j.asr.2020.03.008
[12]
Anderson, D.N., Anghel, A., Yumoto, K., Ishitsuka, M. and Kudeki, E. (2002) Estimating Daytime, Vertical E × B Drift Velocities in the Equatorial F-Region Using Ground-Based Magnetometer Observations. Geophysical Research Letters, 29, 37-1-37-4. https://doi.org/10.1029/2001GL014562
[13]
Anderson, D.N., Anghel, A., Chau,J. and Veliz, O. (2004) Daytime Vertical E × B Drift Velocities Inferred from Ground-Based Magnetometer Observations at Low Latitudes. Space Weather, 2, S11001. https://doi.org/10.1029/2004SW000095
[14]
Yizengaw, E., Moldwin, M.B., Zesta, E., Biouele, C.M., Damtie, B., et al. (2014) The Longitudinal Variability of Equatorial Electrojet and Vertical Drift Velocity in the African and American Sectors. Annals of Geophysics, 32, 231-238. https://doi.org/10.5194/angeo-32-231-2014
[15]
Akala, A.O., Seemala, G.K., Doherty, P.H., Valladares, C.E., Carrano, C.S., Espinoza, J. and Oluyo, S. (2013) Comparison of Equatorial GPS-TEC Observations over an African Station and an American Station during the Minimum and Ascending Phases of Solar Cycle 24. Annals of Geophysics, 31, 2085-2096. https://doi.org/10.5194/angeo-31-2085-2013
[16]
Amaechi, P.O., Oyeyemi, E.O. and Akala, A.O. (2018) Geomagnetic Storm Effects on the Occurrences of Ionospheric Irregularities over the African Equatorial/Low-Latitude Region. Advances in Space Research, 61, 2070-2090. https://doi.org/10.1016/j.asr.2018.01.035
[17]
Paznukhov, V., Carrano, V., Doherty, C.S., Groves, P.H., Caton, K.M., Valladares, R.G., et al. (2012) Equatorial Plasma Bubbles and L-Band Scintillations in Africa during Solar Minimum. Annales Geophysicae, 30, 675-682. https://doi.org/10.5194/angeo-30-675-2012
[18]
Mungufeni, P., Habarulema, J.B. and Jurua, E. (2016) Trends of Ionospheric Irregularities over African Low Latitude Region during Quiet Geomagnetic Conditions. Journal of Atmospheric and Solar Terrestrial Physics, 138, 261-267. https://doi.org/10.1016/j.jastp.2016.01.015
[19]
Yizengaw, E. (2021) Ionospheric Dynamics and Their Strong Longitudinal Dependences, Space Physics and Aeronomy Collection Volume 3: Ionosphere Dynamics and Applications. Geophysical Monograph 260, American Geophysical Union, John Wiley & Sons, Inc., Hoboken. https://doi.org/10.1002/9781119815617.ch17
[20]
Beaujardiére, O. and the C/NOFS Science Definition Team (2004) C/NOFS: A Mission to Forecast Scintillations. Journal of Atmospheric and Solar-Terrestrial Physics, 66, 1573-1591. https://doi.org/10.1016/j.jastp.2004.07.030
[21]
Drob, D.P., Emmert, J.T., Meriwether, J.W., Makela, J.J., Doornbos, E., Conde, M. and Klenzing, J.H. (2015) An Update to the Horizontal Wind Model (HWM): The Quiet Time Thermosphere. Earth and Space Science, 2, 301-319. https://doi.org/10.1002/2014EA000089
[22]
Honoré, M.E., Anad, F., Marie, N.C. and César, M.B. (2017) Sq(H) Solar Variation at Yaoundé-Cameroon AMBER Station from 2011 to 2014. International Journal of Geosciences, 8, 545-562.
[23]
Yizengaw, E., Moldwin, M.B., Mebrahtu, A., Damtie, B., Zesta, E., Valladares, C.E. and Doherty, P. (2011) Comparison of Storm Time Equatorial Ionospheric Electrodynamics in the African and American Sector. Journal of Atmospheric and Solar-Terrestrial Physics, 73, 156-163. https://doi.org/10.1016/j.jastp.2010.08.008
[24]
Yizengaw, E., Zesta, E., Moldwin, M.B., Damtie, B., Mebrahtu, A., et al. (2012) Longitudinal Differences of Ionospheric Vertical Density Distribution and Equatorial Electrodynamics. Journal of Geophysical Research, 117, A07312. https://doi.org/10.1029/2011JA017454
[25]
Scherliess, L. and Fejer, B.G. (1999) Radar and Satellite Global Equatorial F-Region Vertical Drift Model. Journal of Geophysical Research, 104, 6829-6842. https://doi.org/10.1029/1999JA900025
[26]
Manoj, C. and Maus, S. (2012) A Real-Time Forecast Service for the Ionospheric Equatorial Zonal Electric Field. Space Weather, 10, S09002. https://doi.org/10.1029/2012SW000825
[27]
Kaab, M., Benkhaldoun, Z., Fisher, D.J., Harding, B., Bounhir, A., Makela, J.J., et al. (2017) Climatology of Thermospheric Neutral Winds over Oukaïmeden Observatory in Morocco. Annales Geophysicae, 35, 161-170. https://doi.org/10.5194/angeo-35-161-2017
[28]
Amaechi, P.O., Oyeyemi, E.O., Akala, A.O., Falayi, E.O., Kaab, M., Benkhaldoun, Z., et al. (2020) Quiet Time Ionopheric Irregularities over the African Equatorial Ionization Anomaly Region. Radio Science, 55, e2020RS007077. https://doi.org/10.1029/2020RS007077
[29]
Chartier, A.T., Makela, J.J., Liu, H., Bust, G.S. and Noto, J. (2015) Modeled and Observed Equatorial Thermospheric Winds and Temperatures. Journal of Geophysical Research: Space Physics, 120, 5832-5844. https://doi.org/10.1002/2014JA020921
[30]
Link, R. and Cogger, L. (1988) A Reexamination of the OI 6300-Aº Nightglow. Journal of Geophysical Research, 93, 9883-9892. https://doi.org/10.1029/JA093iA09p09883
[31]
Rastogi, R.G. (1994) Westward Equatorial Electrojet during Daytime Hours. Journal of Geophysical Research, 79, 1503-1512. https://doi.org/10.1029/JA079i010p01503
[32]
Richmond, A.D. (1995) Ionospheric Electrodynamics Using Magnetic Apex Coordinates. Journal of Geomagnetism and Geoelectricity, 47, 191-212. https://doi.org/10.5636/jgg.47.191
[33]
Chapman, S. (1951) The Equatorial Electrojet as Detected from the Abnormal Electric Current Distribution above Huancayo, Peru and Elsewhere. Archiv für Meteorologie, Geophysik und Bioklimatologie. Serie A, 4, 368-390. https://doi.org/10.1007/BF02246814
[34]
Anderson, D., Anghel, A., Chau, J.L. and Yumoto, K. (2006) Global, Low-Latitude, Vertical E × B Drift Velocities Inferred from Daytime Magnetometer Observations. Space Weather, 4, S08003. https://doi.org/10.1029/2005SW000193
[35]
Kelley, M.C. (1989) The Earth’s Ionosphere, Plasma Physics and Electrodynamics. International Geophysics Series, 43. Academic Press, Inc., Cambridge.
[36]
Rabiu, A.B., Yumoto, K., Falayi, E.O., Bello, O.R. and MAGDAS/CPMN Group (2011) Ionosphere over Africa: Results from Geomagnetic Field Measurements during International Heliophysical Year IHY. Sun and Geosphere, 6, 61-64.
[37]
Rabiu, A.B., Folarin, O.O., Uozumi, T., Hamid, N.S.A. and Yoshikawa, A. (2017) Longitudinal Variation of Equatorial Electrojet and the Occurrence of Its Counter Electrojet. Annales Geophysicae, 35, 535-545. https://doi.org/10.5194/angeo-35-535-2017
[38]
West, K.H. and Heelis, R.A. (1996) Longitude Variations in Ion Composition in the Morning and Evening Topside Equatorial Ionosphere near Solar Minimum. Journal of Geophysical Research, 101, 7951-7960. https://doi.org/10.1029/95JA03377
[39]
Yamazaki, D., Loughlin, F.O., Trigg, M.A., Miller, Z.F., Pavelsky, T.M. and Bates, P.D. (2014) Development of the Global Width Database for Large Rivers. Water Resources Research, 50, 3467-3480. https://doi.org/10.1002/2013WR014664
[40]
Vichare, G. and Richmond, A.D. (2005) Simulation Study of the Longitudinal Variation of Evening Vertical Ionospheric Drifts at the Magnetic Equator during Equinox. Journal of Geophysical Research—Space Physics, 110, A05304. https://doi.org/10.1029/2004JA010720
[41]
Hagan, M.E. and Forbes, J.M. (2002) Migrating and Nonmigrating Diurnal Tides in the Middle and Upper Atmosphere Excited by Tropospheric Latent Heat Release. Journal of Geophysical Research, 107, ACL 6-1-ACL 6-15. https://doi.org/10.1029/2001JD001236
[42]
Hartman, W.A. and Heelis, R.A. (2007) Longitudinal Variations in the Equatorial Vertical Drift in the Topside Ionosphere. Journal of Geophysical Research, 112, A03305. https://doi.org/10.1029/2006JA011773
[43]
Tesema, F. Mesquita, R., Meriwether, J., Damtie, B., Nigussie, M., Makela, J., et al. (2017) New Results on Equatorial Thermospheric Winds and Temperatures from Ethiopia, Africa. Annales Geophysicae, 35, 333-344. https://doi.org/10.5194/angeo-35-333-2017
[44]
Rabiu, A.B., Okoh, D.I., Wu, Q., Bolaji, O.S., Abdulrahim, R.B., Dare-Idowu, O.E. and Obafaye, A.A. (2021) Investigation of the Variability of Nighttime Equatorial Thermospheric Winds over Nigeria, West Africa. Journal of Geophysical Research: Space Physics, 126, e2020JA028528. https://doi.org/10.1029/2020JA028528
