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VHF radar studies of counter electrojet events during the northern winter solstice period of 1992
Earth, Planets and Space volume 59, pages 259–265 (2007)
Abstract
A sequence of counter electrojet events during the winter solstice period of 1992 are studied along with control quiet day observations at the magnetic equatorial location of Trivandrum (8.5°N, 76.5°E; dip 0.5°N) using VHF (54.95 MHz) coherent backscatter radar observations. Some of the unusual features observed on these days are: (1) an unusual radar signal with reversed Doppler values corresponding to westward electric field, for a brief duration of 5 min at approximately 1330 h, at the higher altitudes 112–117 km on 21 January 1992, as against the usual observation of the signal at lower altitudes below 112 km during CEJ times; (2) type I plasma waves in the late afternoon around 1800 h (after the CEJ event) at altitudes above 101 km (on 21 and 23 January 1992) when the backscattered power is low, indicating the unusual tidal influences on the electric field behavior on certain CEJ days; (3) distortions in the height structure of the vertical polarization electric field, attributed to the modulation of the electrojet altitude structure by action of zonal neutral winds; (4) westward electric field, as seen by the radar, even while the ΔH values are positive.
References
Ananda Rao, B. G. and R. Raghavarao, Structural changes in current fields of the equatorial electrojet due to zonal and meridional winds, J. Geophys. Res., 92, 2514, 1987.
Brown, G. M. and W. R. Williams, Day-to-day variability of Sq(H), Planet. Space Sci., 17, 455–466, 1969.
Crochet, M., C. Hanuise, and P. Broche, HF radar studies of two-stream instability during an equatorial counter electrojet, J. Geophys. Res., 84, 5223, 1979.
Fambitakoye, O. P., P. N. Mayaud, and A. D. Richmond, Equatorial electrojet and daily regular variation SR-III. Comparison of observations with a physical model, J. Atmos. Terr. Phys., 38, 113, 1976.
Farley, D. T., A plasma instability resulting in field aligned irregularities in the ionosphere, J. Geophys. Res., 68, 6083, 1963.
Farley, D. T., Theory of equatorial electrojet plasma waves/: New developments and current status, J. Atmos. Terr. Phys., 47, 729, 1985.
Fejer, B. G. and M. C. Kelly, Ionospheric irregularities, Rev. Geophys. and Space Phys., 18, 401, 1980.
Forbes, J. M., Equatorial electrojet, Rev. Geophys. Space Phys., 19, 469, 1981.
Forbes, J. M. and R. S. Lindzen, Atmospheric solar tides and their electrodynamic effects, I, The global Sq current system, J. Atmos. Terr. Phys., 38, 897, 1976a.
Hauise, C., C. Mazaudier, P. Vila, M. Blanc, and M. Crochet, Global dynamo simulation of ionospheric currents and their connection with the equatorial electrojet: A case study, J. Geophys. Res., 88, 253, 1983.
Last, B. J., D. A. Emilia, and A. K. Outhred, AQD occurrence at Adis Ababa, Trivandrum and Alibag, Planet. Space Sci., 24, 567, 1976.
Mariott, R. T., A. D. Richmond, and S. V. Venkateswaran, On quiet-time equatorial electrojet and counter electrojet, J. Geomagn. Geoelectr., 31, 311, 1979.
Mayaud, P. N., The equatorial counter electrojet—a review of its geomagnetic aspects, J. Atmos. Terr. Phys., 39, 1055, 1977.
Omwumechili, C. A., Study of the return currents of the equatorial electrojet, J. Geomagn. Geoelectr., 44, 1, 1992.
Rastogi, R. G., Westward equatorial electrojet during daytime hours, J. Geophys. Res., 79, 1503, 1974.
Rastogi, R. G., The equatorial electrojet: Magnetic and ionospheric effects, in Geomagnetism, 3 ed., J. A. Jacobs, Academic Press Limited, London, 453, 1989.
Ravindran, S. and C. A. Reddy, Variation of type I plasma wave phase velocity with electron drift velocity in the equatorial electrojet, J. Geophys. Res., 98, 21581, 1993.
Reddy, C. A., The equatorial electrojet and associated plasma instabilities, J. Sci. Indst. Tes., 36, 580, 1977.
Reddy, C. A., Equatorial electrojet—A review of ionospheric and geomagnetic aspects, J. Atmos. Terr. Phys., 43, 557, 1981.
Reddy, C. A., The equatorial electrojet, Pure Appl. Geophys., 131, 485, 1989.
Reddy, C. A. and C. V. Devasia, Height and latitude structure of electric fields and currents due to local east-west winds in the equatorial elec-trojet, J. Geophys. Res., 86, 5751, 1981.
Reddy, C. A., V. V. Somayajulu, and K. S. Viswanathan, The lunar phase and the equatorial electrojet, In low latitude aeronomical processes, Proceedings of Symposium, Bangalore, India, May 29–June 9, 1979.
Reddy, C. A., B. T, Vikramkumar, and K. S. Viswanathan, Electric fields and currents in the equatorial electrojet deduced from VHF radar observations — I. A method of estimating electric fields, J. Atmos. Terr. Phys., 49, 183, 1987.
Reid, G. C., The formation of small-scale irregularities in the ionosphere, J. Geophys. Res., 73, 1627, 1968.
Richmond, A. D., Equatorial electrojet. I. Development of a model including winds and instabilities, J. Atmos. Terr. Phys., 35, 1083–1103, 1973a.
Sastri, J. H., Phase variability of Sq(H) on normal quiet days in the equatorial electrojet region, Geophys. J. Roy. Astr. Soc., 71, 187, 1982.
Schieldge, J. P., S. V. Venkateswaran, and A. D. Richmond, The ionospheric dynamo and equatorial magnetic variations, J. Atmos. Terr. Phys., 35, 1045, 1973.
Somayajulu, Behavior of harmonic components of the geomagnetic field during counter electrojet events, J. Geomagn. Geoelectr., 40, 111–130, 1988.
Somayajulu, V. V. and K. S. Viswanathan, Radar observations during equatorial counter electrojet events, Indian J. Rad. and Space Phys., 16, 350, 1987.
Somayajulu. V. V., K. S. Viswanathan, K. S. V. Subbarao, and Ligi Cherian, Distortions in the height structure of the equatorial electrojet, J. Atmos. Terr. Phys., 56, 41, 1994.
Stening, R. J., Analysis of contributions to ionospheric dynamo currents from emf’s at different latitudes, Planet. Space Sci., 25, 587, 1977a.
Stening, R. J., Magnetic variations at other latitudes during reversed equatorial electrojet, J. Atmos. Terr. Phys., 39, 1071, 1977b.
Stening, R. J., What drives the equatorial electrojet, J. Atmos. Terr. Phys., 57, 1117, 1995.
Viswanathan, K. S., Study of electrodynamics of the equatorial electrojet, Ph. D. thesis, University of Kerala, India, 99–118, 1986.
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Manju, G., Viswanathan, K.S. VHF radar studies of counter electrojet events during the northern winter solstice period of 1992. Earth Planet Sp 59, 259–265 (2007). https://doi.org/10.1186/BF03353103
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DOI: https://doi.org/10.1186/BF03353103