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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 24, issue 6
Ann. Geophys., 24, 1567–1580, 2006
https://doi.org/10.5194/angeo-24-1567-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 24, 1567–1580, 2006
https://doi.org/10.5194/angeo-24-1567-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.

  03 Jul 2006

03 Jul 2006

Study of spatial and temporal characteristics of L-band scintillations over the Indian low-latitude region and their possible effects on GPS navigation

P. V. S. Rama Rao, S. Gopi Krishna, K. Niranjan, and D. S. V. V. D. Prasad P. V. S. Rama Rao et al.
  • Space Physics Laboratories, Department of Physics, Andhra University, Visakhapatnam 530 003, India

Abstract. The scintillation data (S4-index) at the L-band frequency of 1.575GHz, recorded from a total of 18 GPS receivers installed at different locations in India under the GAGAN project, have provided us with a unique opportunity, for the first time in the Indian region, to make a simultaneous study of spatio-temporal and intensity characteristics of the trans-ionospheric scintillations during the 18-month, low sunspot activity (LSSA) period from January 2004 to July 2005. During this period, the occurrence of scintillations is found to be maximum around the pre-midnight hours of equinox months, with very little activity during the post-midnight hours. No significant scintillation activity is observed during the summer and winter months of the period of observation. The intensity (S4 index) of the scintillation activity is stronger around the equatorial ionization anomaly (EIA) region in the geographic latitude range of 15° to 25° N in the Indian region. These scintillations are often accompanied by the TEC depletions with durations ranging from 5 to 25 min and magnitudes from 5 to 15 TEC units which affect the positional accuracy of the GPS by 1 to 3 m. Further, during the intense scintillation events (S4>0.45≈10 dB), the GPS receiver is found to lose its lock for a short duration of 1 to 4 min, increasing the error bounds effecting the integrity of the SBAS operation. During the present period of study, a total of 395 loss of lock events are observed in the Indian EIA region; this number is likely to increase during the high sunspot activity (HSSA) period, creating more adverse conditions for the trans-ionospheric communications and the GPS-based navigation systems.

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