Daytime Vertical E×B Drift Velocities Inferred from Ground-Based Equatorial Magnetometer Observations

  • David AndersonEmail author
Part of the IAGA Special Sopron Book Series book series (IAGA, volume 2)


The daytime equatorial electrojet is a narrow band of enhanced eastward current flowing in the 100–120 km altitude region within ±2° latitude of the dip equator. A unique way of determining the daytime strength of the electrojet is to observe the difference in the magnitudes of the Horizontal (H) component between a magnetometer placed directly on the magnetic equator and one displaced 6–9° away. The difference between these measured H values provides a direct measure of the daytime electrojet current, and in turn, the magnitude of the vertical E×B drift velocity in the F region ionosphere. This paper emphasizes two major topics related to the title: (1) Describes and summarizes the techniques developed for obtaining the daytime, E×B drift velocities from ground-based magnetometer observations, and (2) Describes and summarizes the equatorial, ionospheric physical transport mechanisms that have been addressed using these techniques.


Total Electron Content Drift Velocity Magnetic Equator Equatorial Electrojet Incoherent Scatter Radar 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank Dr. Koki Chau, Director of the Jicamarca Radio Observatory, for providing the Jicamarca and Piura magnetometer data. The Jicamarca Radio Observatory is a facility of the Instituto Geofisico del Peru, Ministry of Education, and is operated with support from the NSF Cooperative agreement ATM-o432565. We also thank Prof. Kiyo Yumoto, Dept. of Earth and Planetary Sciences, Kyushu University, Fukuoka, Japan for supplying the Davao and Muntinlupa magnetometer observations.


  1. Anderson DN (1973) A theoretical study of the ionospheric, F-region equatorial anomaly, I. Theory, planet. Space Sci 21:409–419CrossRefGoogle Scholar
  2. Anderson D, Anghel A, Araujo EA, Valladares C, Lin C (2006a) Theoretically modeling the low-latitude, ionospheric response to large magnetic storms. Radio Sci 41:RS5S04. http://doi:10.1029/2005RS003376 CrossRefGoogle Scholar
  3. Anderson D, Anghel A, Chau J, Veliz O (2004) Daytime vertical E×B drift velocities inferred from ground-based magnetometer observations at low latitudes. Space Weather 2:S11001. http://doi:10.1029/2004SW000095 CrossRefGoogle Scholar
  4. Anderson D, Anghel A, Chau J, Yumoto K (2006b) Global, low-latitude, vertical E×B drift velocities inferred from daytime magnetometer observations. Space Weather 4:S08003. http://doi:10.1029/2005SW000193 CrossRefGoogle Scholar
  5. Anderson D, Anghel A, Yumoto K, Ishitsuka M, Kudeki E (2002) Estimating daytime vertical E×B drift velocities in the equatorial F-region using ground-based magnetometer observations. GRL 29(12):1596. http://doi:10.1029/2001GL014562 CrossRefGoogle Scholar
  6. Anderson D, Araujo-Pradere EA, Scherliess L (2009) Comparing daytime, equatorial E×B drift velocities and TOPEX/TEC observations associated with the 4-cell, non-migrating tidal structure. Ann Geophys 7:1–7Google Scholar
  7. Anderson DN, Klobuchar JA, Doherty PH, Rastogi RG (1992) A comparison of theoretical modeling of the low latitude ionosphere against TEC data from the indian longitudes during solar minimum. Int Beacon Symposium, MIT, Boston, MAGoogle Scholar
  8. Anghel A, Anderson DN, Maruyama N, Chau J, Yumoto K, Bhattacharyya A, Alex S (2007) Interplanetary electric fields and their relationship to low-latitude electric fields under disturbed conditions. J Atmos Solar-Terr Phys 69:1147–1159CrossRefGoogle Scholar
  9. Balsley BB (1964) Evidence of a stratified echoing regions at 150 kilometers in the vicinity of magnetic equator during daylight hours. JGR 69:1925CrossRefGoogle Scholar
  10. Blanc E, Mercandalli B, Houngninou E (1996) Kilometric irregularities in the E and F regions of the daytime equatorial ionosphere observed by a high resolution HF radar. GRL 23:645CrossRefGoogle Scholar
  11. Chau JL (1998) Examination of various techniques for measuring wind velocities using clear-air radars, with emphasis on vertical wind measurements. Ph.D Thesis, University of Colorado at BoulderGoogle Scholar
  12. Chau JL, Fejer BG, Goncharenko LP (2009) Quiet variability of equatorial E×B drifts during sudden stratospheric warming events. Geophys Res Lett 36:L05101. http://doi:10.1029/2008GL36785 CrossRefGoogle Scholar
  13. England SL, Maus S, Immel TJ, Mende SB (2006) Longitudinal variation of the E-region electric fields caused by atmospheric tides. Geophys Res Lett 33:L21105. http://doi:10.1029/2006GL027465 CrossRefGoogle Scholar
  14. Fang TW, Richmond AD, Liu JY, Maute A (2008a) Wind dynamo effects on ground magnetic perturbations and vertical drifts. J Geophys Res 113:A11313. http://doi:10.1029/2008JA013513 CrossRefGoogle Scholar
  15. Fang TW, Richmond AD, Liu JY, Maute A, Lin CH, Harper B (2008b) Model simulation of the equatorial electrojet in the Peruvian and Philippine sectors. J Atmos Solar-Terr Phys 70:2203–2211CrossRefGoogle Scholar
  16. Fejer BG (1991) Low latitude electrodynamic plasma drifts: a review. J Atmos Solar-Terr Phys 53:677–693CrossRefGoogle Scholar
  17. Forbes JM (1981) The equatorial electrojet. Rev Geophys 19:469–504CrossRefGoogle Scholar
  18. Fuller-Rowell TJR, Akmaev RA, Wu F, Anghel AF, Maruyame N, Anderson DN, Codrescu MV, Iredell M, Moorthi S, Juang H-M, Hou Y-T, Milllward G (2008) Impact of terrestrial weather on the upper atmosphere. Geophys Res Lett 35:L09808. http://doi:10.1029/2007GL032911 CrossRefGoogle Scholar
  19. Hanson WB, Moffett RJ (1966) Ionization transport effects in the equatorial F region. J Geophys Res 71:5559–5572Google Scholar
  20. Kelley MC, Nicolls MJ, Anderson D, Anghel A, Chau JL, Sekar R, Subbaro KSV, Bhattacharyya A (2007) Multi-longitude case studies comparing the interplanetary and equatorial ionospheric electric fields using an empirical model. J Atmos Solar-Terrestr Phys 69:1174–1181CrossRefGoogle Scholar
  21. Kudeki E, Fawcett C (1993) High resolution observations of 150 km echoes at Jicamarca. GRL 18:1987CrossRefGoogle Scholar
  22. Manoj C, Luhr H, Maus S, Nagarajan N (2006) Evidence for short spatial correlation lengths of the noon-time equatorial electrojet – inferred from a comparison of satellite and ground magnetic data. J Geophys Res 111:A11312. http://doi:10.1029/2006JA011855 CrossRefGoogle Scholar
  23. Maruyama N, Sazykin S, Spiro R, Andearson D, Anghel A, Wolf RA, Toffoletto FR, Fuller-Rowell TJ, Codrescu MV, Richmond AD, Millward G (2007) Modeling storm-time electrodynamics of the low-latitude ionosphere-thermosphere system: can long lasting disturbance electric fields be accounted for? J Atmos Solar-Terr Phys 69:1182–1199CrossRefGoogle Scholar
  24. Nicolls MJ, Kelley MJ, Chau JL, Veliz O, Anderson D, Anghel A (2007) The spectral properties of low latitude daytime electric fields inferred from magnetometer observations. J Atmos Solar-Terr Phys 69:1160–1173CrossRefGoogle Scholar
  25. Rastogi RG, Klobuchar JA (1990) Ionospheric electron content within the equatorial F2 layer anomaly belt. JGR 95:19045–19052CrossRefGoogle Scholar
  26. Reddy CA (1989) The equatorial electrojet. PAGEOPH 131:485–508CrossRefGoogle Scholar
  27. Richmond AD (1989) Modeling the ionospheric wind dynamo: a review. PAGEOPH 131:413–435CrossRefGoogle Scholar
  28. Scherliess L, Fejer BG (1999) Radar and satellite global equatorial F region vertical drift model. JGR 104:6829–6842CrossRefGoogle Scholar
  29. Scherliess L, Thompson DC, Schunk RW (2008) Longitudinal variability of low-latitude total electron content: tidal influences. J Geophys Res 113:A01311. http://doi:10.1029/2007JA012480 CrossRefGoogle Scholar
  30. Stolle C, Manoj C, Luhr H, Maus S Alken P (2008) Estimating the daytime equatorial ionization anomaly strength from electric field proxies. J Geophys Res 113:A09310. http://doi:10.1029/2007JA012781 CrossRefGoogle Scholar
  31. Tsunoda RT, Ecklund WL (2000) On the nature of 150-km radar echoes over the magnetic dip equator. GRL 27:657–660CrossRefGoogle Scholar
  32. Wang W, Lei J, Burns AG, Wiltberger M, Richmond AD, Solomon SC, Killeen TL, Talaat ER, Anderson DN (2008) Ionospheric electric field variations during a geomagnetic storm simulated by a coupled magnetosphere ionosphere thermosphere (CMIT) model. Geophys Res Lett 15:L18105. http://doi:10.1029/2008GL035155 CrossRefGoogle Scholar
  33. Woodman RF, Villanueva F (1995) Comparisons of electric fields measured at F-region heights with 150 km – irregularity drift measurements. Paper presented at the 9th international symposium on equatorial aeronomy, Bali, IndonesiaGoogle Scholar

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© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.Cooperative Institute for Research in Environmental Sciences, University of ColoradoBoulderUSA
  2. 2.Space Weather Prediction Center, National Oceanic and Atmospheric AdministrationBoulderUSA

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