Abstract
Features of the equatorial electrojet are studied at Sao Luiz (2.6°S, 44.2°W, inclination −0.25°) in eastern Brazil and Sikasso (11.3°N, 5.7°W, inclination 0.1°) in the western African sector. The stations are situated on either side of the lowest magnetic field intensity in the region of rapid changes in the declination. The daily variations of ΔX at the two stations are almost similar with the peak around noon with maximum values during equinoxes and minimum values during J-solstices. Daily variations of ΔY differ with the maximum deviation of about −35 nT around noon at Sao Luiz and much smaller value of about −10 nT around 14 h LT for Sikasso. The direction of the H vector varies from 15°W of north at 08 h to more than 30°W of north at 17 h for Sao Luiz and from 14°E of north to 25°W of north at 18 h for Sikasso. The plot of the deviations in ΔX and ΔY at different hours for the two stations shows the points along narrow ellipses with major axis aligned along 22°W of north for Sao Luiz and along 3°W of north for Sikasso as compared to declination of 20°W for Sao Luiz and 6°W for Sikasso. The deviations in ΔX at the two stations are fairly well correlated.
Similar content being viewed by others
References
Anandarao B G and Raghavarao R 1987 Structural changes in the currents and fields of the equatorial electrojet due to zonal and meridional winds; J. Geophys. Res. 92 2514–2526.
Arora B R, Mahashabde M V and Kalra R 1993 Indian IEEY geomagnetic observational program and some preliminary results; Rev. Bras. Geofis. 11 365–385.
Baker W G and Martyn D F 1953 Electric currents in the ionosphere, 1, the conductivity; Phil. Trans. Roy. Soc. A246 281–294.
Chapman S 1951 The equatorial electrojet as detected from the abnormal electric current distribution above Huancayo, Peru and elsewhere; Arch. Meteorol. Geophys. Bioklimatol. A4 368–390.
Doumouya V, Vassal J, Cohen Y, Fambitakoye O and Menvielle M 1998 Equatorial electrojet at African longitudes: First results from magnetic measurements; Ann. Geophys. 16 658–676.
Gangepain J, Crochet M and Richmond A D 1977 Comparison of equatorial electrojet models; J. Atmos. Terr. Phys. 39 1119–1124.
Fambitakoye O and Mayaud P N 1976a Equatorial electrojet and regular daily variations of SR-I. A determination of the equatorial electrojet parameters; J. Atmos. Terr. Phys. 38 1–17.
Fambitakoye O and Mayaud P N 1976b Equatorial electrojet and regular daily Variations SR-II. The Centre of the equatorial electrojet; J. Atmos. Terr. Phys. 38 19–26.
Forbes J M 1981 The equatorial electrojet; Rev. Geophys. Space Phys. 19 469–504.
Forbes J M and Lindzen R S 1976 Atmospheric solar tides and their electromagnetic effects, II, The equatorial electrojet; J. Atmos. Terr. Phys. 38 911–920.
Forbush S and Casaverde M 1961 Equatorial electrojet in Peru; Carnegie Institution of Washington, Report No. 620.
Hirono M 1952 A theory of diurnal magnetic variations in equatorial regions and conductivity of the ionospheric E region; J. Geomagn. Geoelectr. 4 7–21.
Onwumechili C A, Kawasaki K and Akasofu S I 1973 Relationship between the equatorial electrojet and polar magnetic variations; Planet. Space Sci. 21 1–16.
Rastogi R G 1962 Longitudinal variation in the equatorial electrojet; J. Atmos. Terr. Phys. 24 1031–1040.
Rastogi R G 1972 Sudden disappearance of Es-q and the reversal of equatorial electric Fields; Ann. Geophys. 28 717–728.
Rastogi R G 1975 On the simultaneous existence of eastward and westward flowing equatorial electrojet currents; Proc. Indian Acad. Sci. 78 80–92.
Rastogi R G 1978 Theory of preliminary negative impulses in SSC in H at equatorial Stations; Proc. Indian Acad. Sci. 87 57–60.
Rastogi R G 1999 Ionospheric current system in Indo-Russian longitude sector; Sci. Cult. 65 269–282.
Rastogi R G 1989 The equatorial electrojet: Magnetic and ionospheric effects; In: Geomagnetism (ed.) Jacobs J, Academic Press 3 461–425.
Rastogi R G 2006 Sq and sfe currents at equatorial stations along the western and eastern African sectors; Earth Planets Space 58 1475–1478.
Rastogi R G and Chandra H 1974 Interplanetary magnetic field and the equatorial Ionosphere; J. Atmos. Terr. Phys. 36 377–379.
Rastogi R G and Chandra H 2002 Equatorial electrojet current flow directions; J. Indian Geophys. Union 6 169–174.
Rastogi R G and Iyer K N 1976 Quiet day variation of geomagnetic H field at low Latitudes; J. Geomagn. Geoelectr. 36 377–379.
Rastogi R G and Patel V L 1975 Effect of interplanetary magnetic field on ionosphere over the magnetic equator; Proc. Indian Acad. Sci. 82 121–141.
Rastogi R G and Trivedi N B 2009 Asymmetries in the equatorial electrojet around N-E Brazil sector; Ann. Geophys. 27 1–17.
Rastogi R G, Chandra H and Misra R K 1971 Effect of magnetic activity on electron drifts in the equatorial electrojet region; Nature 233 13–15.
Rastogi R G, Chandra H, Chakrabarty D K, Kitamura K and Yumuto K 2007 Day-to-day correlation of equatorial electrojet at two stations separated by 2000 km in Central South America; Ann. Geophys. 25 1–6.
Rastogi R G, Chandra H, James M E, Kitamura K and Yumuto K 2008 Characteristics of equatorial electrojet in Central South America; Earth Planets Space 60 623–632.
Rastogi R G, Chandra H and Yumuto K 2010 Equatorial electrojet in East Brazil longitudes; J. Earth Syst. Sci. 119 497–505.
Reddy C A 1989 The equatorial electrojet; PAGEOPH 131 485–508.
Richmond A D 1973 Equatorial electrojet, 1, Development of a model including winds and instabilities; J. Atmos. Terr. Phys. 36 1083–1103.
Ronchi C, Sudan R N and Similon P L 1990 Effect of short-scale turbulence on kilometer wavelength irregularities in the equatorial electrojet; J. Geophys. Res. 95 189–200.
Sarabhai V and Nair K N 1971 Morphology of the geomagnetic field variations and a study of the interplanetary magnetic field fluctuations in relation to the daily variations of the geomagnetic field at low latitudes; Cosmic Electrodyn. 2 3–21.
Sugiura M and Cain V C 1966 A model equatorial electrojet; J. Geophys. Res. 71 1869–1877.
Sugiura M and Poros D J 1969 An improved model equatorial electrojet; J. Geophys. Res. 74 4026–4034.
Untiedt J 1967 A model of the equatorial electrojet including meridional currents; J. Geophys. Res. 72 5799–5810.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Rastogi, R.G., Chandra, H., Trivedi, N.B. et al. Equatorial electrojet in the south Atlantic anomaly region. J Earth Syst Sci 120, 301–310 (2011). https://doi.org/10.1007/s12040-011-0050-0
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12040-011-0050-0