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Volume 57 Supplement 3

Special Issue: Special Section for the 2004 off the Kii peninsula earthquakes (1)

Response of the equatorial electrojet to solar flare related X-ray flux enhancements

Abstract

The response of ionospheric E-region electric fields and currents to solar flare related X-ray flux enhancements are studied at the magnetic equatorial location of Trivandrum (8.5°N, 77°E; dip 0.5°N) using VHF (54.95 MHz) coherent backscatter radar observations in the altitude region of 95–110 km conducted during daytime. The amplitude of the Solar Flare Effects (SFE) observed in the earth’s magnetic field variations at Trivandrum have been examined in relation to that at Alibag and it is found that the ratio of the SFE amplitudes at the two stations lies in the range of 1.8–2.6. The backscattered power of the VHF radar showed a substantial reduction during the peak phase of all the strong X-rank flares studied. It has also been observed that there is a sharp fall in the ratio of the field line integrated Hall conductivity (σ2) to the field line integrated Pedersen conductivity (σ1) in the dynamo region during strong flare times in relation to normal times. The time variations of mean Doppler frequency (f D ) of the backscattered signals have been observed to indicate a fall close to the peak phase of the strong flare events. Another new result is the radar observed presence of westward electric field for a long duration of 2–3 hours during a partial counter electrojet (CEJ) event that occurred on one of the days (8 July 1992) studied. The implications of the observations are discussed in detail.

References

  • Balsley, B. B., Electric fields in the equatorial ionosphere: A review of techniques and measurements, J. Atmos. Terr. Phys., 35, 1035–1044, 1973.

    Article  Google Scholar 

  • Banks, P. M. and G. Kockarts, Aeronomy, Part A., Academic press, New York, 1973.

    Google Scholar 

  • Chapman, S., Regular motions in the ionosphere: Electric and magnetic relationships, Bull. Amer. Meteorol. Soc., 42, 85, 1961.

    Google Scholar 

  • Donelly, R. F., An analysis of sudden ionospheric disturbances associated with the proton flare of 1522 UT, Aug. 28, 1966, ESSA Tech. Rep. ERL 92-SDL6, U. S. Government printing office, Washington, D. C., 1968.

    Google Scholar 

  • Farley, D. T. and B. B. Balsley, Instabilities in the equatorial electrojet, J. Geophys. Res., 78, 227, 1973.

    Article  Google Scholar 

  • Fejer, B. G. and M. C. Kelly, Ionospheric irregularities, Rev. Geophys. And Space Phys., 18, 401, 1980.

    Article  Google Scholar 

  • Mitra, A. P. and S. D. Despande, Flaretime models of ionisation profiles in the D region, Space Research XII, Akademic, Verlag, Berlin, 1291, 1972.

    Google Scholar 

  • Mitra, A. P. and C. V. Subrahmanyam, Sudden ionospheric disturbances, Ind. J. Rad. Space Phys., 1, 93, 1972.

    Google Scholar 

  • Oshio, M., N. Fukushima, and T. Nagata, Solar flare effects on geomagnetic field, Rep. Ionos. Space Res. Japan, 21, 77–114, 1967.

    Google Scholar 

  • Rangarajan, G. K. and R. G. Rastogi, Solar flare effect in equatorial magnetic field during morning counter electrojet, Ind. J. Rad. Space Phys., 10, 190–192, 1981.

    Google Scholar 

  • Rastogi, R. G., Solar flare effects on zonal and meridional currents at the equatorial electrojet station, Annamalainagar, J. Atmos. Terr. Phys., 58, 1413–1420, 1996.

    Article  Google Scholar 

  • Rastogi, R. G., M. R. Deshpande, and N. S. Sastri, Solar flare effect in equatorial counter electrojet current, Nature (London), 258, 218–219, 1975.

    Article  Google Scholar 

  • Rastogi, R. G., D. R. K. Rao, S. Alex, B. M. Pathan, and T. S. Sastry, An intense SFE and SSC event in geomagnetic H, Y and Z fields at the Indian Observatories, Ann. Geophys., 15, 1301–1308, 1997.

    Article  Google Scholar 

  • Rastogi, R. G., B. M. Pathan, D. R. K. Rao, T. S. Sastry, and J. H. Sastri, Solar flare effects on the geomagnetic elements during normal and counter electrojet periods, Earth Planets Space, 51, 947–957, 1999.

    Article  Google Scholar 

  • Reddy, C. A., V. V. Somayajulu, and K. S. Viswanathan, The lunar phase and the equatorial electrojet, Low latitude aeronomical processes, COSPAR Symp. Ser., edited by A. P. Mitra, Pergamon, New York, 29, 1980.

    Google Scholar 

  • 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.

    Article  Google Scholar 

  • Richmond, A. D., Equatorial electrojet. I. Development of a model including winds and instabilities, J. Atmos. Terr. Phys., 35, 1083–1103, 1973a.

    Article  Google Scholar 

  • Richmond, A. D., Equatorial electrojet. II. Use of the model to study the equatorial ionosphere, J. Atmos. Terr. Phys., 35, 1105–1118, 1973b.

    Article  Google Scholar 

  • Sampath, S. and T. S. G. Sastry, Results from in situ measurements of ionospheric currents in the equatorial region, J. Geomag. Geoelectr., 31, 373, 1979.

    Article  Google Scholar 

  • Sastri, J. H., The geomagnetic solar flare effect of 6 July 1968 and its implications, Ann. Geophys., 31, 481, 1975.

    Google Scholar 

  • Sato, T., The response of the lower ionosphere to the great solar flare of August 7, 1972, J. Geomag. Geoelectr., 27, 383, 1975.

    Article  Google Scholar 

  • Srivastava, B. J., The geomagnetic solar flare effect of 03 May 1973 at Indian stations and its dependence on the counter electrojet, J. Atmos. Terr. Phys., 36, 1571, 1974.

    Article  Google Scholar 

  • Subbaraya, B. H., S. Prakash, and S. P. Gupta, Electron densities in the equatorial lower ionosphere from the Langmuir probe experiments conducted at Thumba during the years 1966–1978, ISRO-PRL Special Report, ISRO-PRL-SR-15-83, 1983.

    Google Scholar 

  • Thome, G. D. and L. S. Wagner, Electron density enhancements in the E and F regions of the ionosphere during solar flares, J. Geophys. Res., 76, 6883, 1971.

    Article  Google Scholar 

  • Van Sabben, D., Solar flare effects and simultaneous magnetic daily variation, J. Atmos. Terr. Phys., 30, 1641, 1968.

    Article  Google Scholar 

  • Viswanathan, K. S., Study of electrodynamics of the equatorial electrojet, Ph.D. thesis, University of Kerala, India, 1986.

    Google Scholar 

  • Yasuhara, M. and H. Maeda, Geomagnetic Crochet of 15 November 1960, J. Atmos. Terr. Phys., 21, 289, 1961.

    Article  Google Scholar 

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Correspondence to G. Manju.

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Manju, G., Viswanathan, K.S. Response of the equatorial electrojet to solar flare related X-ray flux enhancements. Earth Planet Sp 57, 231–242 (2005). https://doi.org/10.1186/BF03351819

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Key words

  • Equatorial electrojet
  • solar flare effect
  • magnetic crochet
  • radar
  • conductivity