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Morphological and spectral characteristics of L-band and VHF scintillations and their impact on trans-ionospheric communications

Abstract

Amplitude scintillations recorded at 1.5 GHz frequency during the high (1998–1999) and low (2004–2005) sunspot activity periods over a low latitude station, Waltair (17.7°N, 83.3°E) revealed that the L-band scintillations mostly occur during the post-sunset to midnight hours peaking around 21:00 hr local time with maximum occurrence during equinoxes, moderate during winter and minimum during the summer months. The occurrence, as well as the intensity of scintillations, is found to be strongly dependant on both the season of the year and the sunspot number. Strong (S4-index >0.45) and fast fading scintillations (fading rates >40 fads/min) observed during the post-sunset hours of equinoxes and winter months manifest as several short duration patches at both VHF (244 MHz) and L-band (1.5 GHz) frequencies and are found to be always associated with the range or total Spread-F on ionograms and bubbles/depletions in the Total Electron Content (TEC) measured from a colocated dual frequency GPS receiver, suggesting that these scintillations are of the Plasma Bubble Induced (PBI) type. On the other hand, relatively weak and slow fading scintillations (fading rates <8 fads/min) observed around the post-midnight hours of the summer months which appear as long-duration patches (>3 hr) at 244 MHz signal (with practically no scintillation activity at the L-band frequencies) are often found to be associated with frequency Spread-F on ionograms with no depletions in TEC. Further, the presence of Fresnel oscillations observed in the spectrum of 244 MHz suggests that the long-duration scintillations observed are due to the presence of a thin layer of irregularities in the bottom side F-region which are generally known as Bottom Side Sinusoidal (BSS) irregularities. Further, the PBI-type scintillations at L-band frequencies are often found to exceed 10 dB power levels (S4 > 0.45) even during the low sunspot activity period of 2004–2005, and cause Loss of Lock in the GPS receivers resulting in a total interruption in the received signals.

References

  • Aarons, J., Global morphology of ionospheric scintillation, Proc. IEEE, 70, 360–378, 1982.

    Article  Google Scholar 

  • Aarons, J., J. P. Mullen, H. E. Whitney, and E. M. Mackenzie, The Dynamics of Equatorial Irregularity Patch Formation, Motion and Decay, J. Geophys. Res., 85, 139–149, 1980.

    Article  Google Scholar 

  • Anderson, D. N. and G. Haerendel, The motion of depleted plasma regions in the equatorial ionosphere, J. Geophys. Res., 16, 939–945, 1979.

    Google Scholar 

  • Bandhyopadhyay, T., A. Guha, A. Das Gupta, P. Banerjee, and A. Bose, Degradation of navigational accuracy with Global Positioning System during periods of scintillation at equatorial latitudes, Electron. Lett., 33, 1010–1011, 1997.

    Article  Google Scholar 

  • Basu, S., Su. Basu, C. E. Valladares, A. Das Gupta, and H. E. Whitney, Scintillations associated with bottomside sinusoidal irregularities in the equatorial F-region, J. Geophys. Res., 91, 270–276, 1986.

    Article  Google Scholar 

  • Bhattacharyya, A., S. Basu, K. M. Groves, C. E. Valladares, and R. Shee-han, Dynamics of equatorial F region irregularities from spaced receiver scintillation observations, Geophys. Res. Lett., 28, 119–122, 2001.

    Article  Google Scholar 

  • Briggs, B. H. and I. A. Parkin, On the variation of radio star and satellite scintillations with zenith angle, J. Atmos. Terr. Phys., 25, 339–365, 1963.

    Article  Google Scholar 

  • Calvert, W. and R. Cohen, The interpretation and synthesis of certain Spread-F configuration appearing on equatorial ionograms, J. Geophys. Res., 66, 3125, 1961.

    Article  Google Scholar 

  • Ciraolo, L. and P. Spalla, Comparison of ionospheric total electron content from the Navigation Satellite System and the GPS, Radio Sci., 32, 1071–1080, 1997.

    Article  Google Scholar 

  • Costa, E. and M. C. Kelly, On the role of steepened structures and drift waves in equatorial Spread-F, J. Geophys. Res., 83, 4359–4364, 1978.

    Article  Google Scholar 

  • Das Gupta, A., Basu, S., J. Aarons, J. A. Klobuchar, Basu, Su., and A. Bushby, VHF amplitude scintillations and associated electron content depletions as observed at Arequipa, Peru, J. Atmos. Terr. Phys., 45, 15–26, 1983.

    Article  Google Scholar 

  • Das Gupta, A., S. Rat, A. Paul, P. Banerjee, and A. Bose, Errors in position-fixing by GPS in an environment of strong equatorial scintillations in the Indian zone, Radio Sci., 39, (RS1S30), doi:10.1029/ 2002RS002822, 2004.

    Google Scholar 

  • Davies, K. and G. K. Hartmann, Studying the ionosphere with Global Positioning System, Radio Sci., 32, 1695–1703, 1997.

    Article  Google Scholar 

  • Goodwin, G. L., J. H. Silby, K. J. W Lynn, A. M. Breed, and E. A. Essex, Total electron content and ionospheric slab thickness measurements using GPS satellites, Proc. South Pacific Solar-Terrestrial Physics Workshop, Tenth National Congress of the Australian Institute of Physics, Univ. of Melbourne, Melbourne, Australia, 1992.

  • Kelley, M. C, The Earth’s Ionosphere, Academic Press, San Diego, 1989.

    Google Scholar 

  • Krishna Moorthy, K., C. Ragha Reddi, and B. V. Krishna Murthy, Nighttime ionospheric scintillations at the magnetic equator, J. Atmos. Terr. Phys., 41, 123–134, 1979.

    Article  Google Scholar 

  • Rama Rao, P. V. S., K. Niranjan, D. S. V. V. D. Prasad, S. Gopi Krishna, and S. Tulasi Ram, Simultaneous Observations of VHF and L-band Scintillations from an Indian Low Latitude Station, Waltair (17.7°N, 83.3°E), Proc. of IBSS-2004, Trieste, Italy, 2004.

    Google Scholar 

  • Rufenach, C. L., Power law wave number spectrum deduced from ionospheric scintillation observations, J. Geophys. Res., 77, 4761–4772, 1972.

    Article  Google Scholar 

  • Whitney, H. E., Notes on the relationship of scintillation index to probability distribution and their uses for system design, Rep. AFCRL-TR-74-0004, Air Force Cambridge Res. Lab., Hanscom Air Forse Base, Mass, 1974. Whitney, H. E., J. Aarons, and C. Malik, A proposed index for measuring ionospheric scintillations, Planet. Space Sci., 17, 1069–1073, 1969.

    Google Scholar 

  • Woodman, R. F and C. Lahoz, Radar observations of F-region equatorial irregularities, J. Geophys. Res., 81, 5447–5466, 1976.

    Article  Google Scholar 

  • Yeh, K. C. and C. H. Liu, Radio wave scintillations in the ionosphere, Proc. IEEE, 70, 324–360, 1982.

    Article  Google Scholar 

  • Yeh, K. C, H. Soicher, C. H. Liu, and E. Borelli, Ionospheric bubbles observed by the Faraday rotation method at Natal, Brazil, Geophys. Res. Lett., 6, 473–475, 1979.

    Article  Google Scholar 

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Correspondence to P. V. S. Rama Rao.

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Rama Rao, P.V.S., Tulasi Ram, S., Gopi Krishna, S. et al. Morphological and spectral characteristics of L-band and VHF scintillations and their impact on trans-ionospheric communications. Earth Planet Sp 58, 895–904 (2006). https://doi.org/10.1186/BF03351994

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  • DOI: https://doi.org/10.1186/BF03351994

Keywords

  • Global Position System
  • Total Electron Content
  • Sunspot Number
  • Global Position System Receiver
  • Vertical Total Electron Content