Latitudinal variation in the occurrence of GPS L-band scintillations associated with the day-to-day changes in TEC, h'F and the ExB drift velocity and their impact on GPS satellite signals

Autor(es)

Venkatesh, K. ; Rao, P. V. S. Rama ; Seemala, Gopi K. ; Prasad, D. S. V. V. D.

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF EARTH SYSTEM SCIENCE; v. 124, n. 3, p. 17-pg., 2015-04-01.

Resumo

The present study describes the day-to-day variations in the occurrence of GPS L-band scintillations from equator to the anomaly crest location associated with the changes in TEC, hF and E xB drift velocities. The GPS-TEC and S-4 index data from an equatorial station, Trivandrum (8.47(a similar to)N, 76.91(a similar to)E), a low latitude station, Waltair (17.7(a similar to)N, 83.3(a similar to)E) and an anomaly crest location Kolkata (22.6(a similar to)N, 88.4(a similar to)E) during the low solar activity years of 2004 and 2005 are used. It is observed that the day-time ambient TEC is higher during scintillation days compared to that during the days on which there are no scintillations at the three different locations mentioned above. Further, the diurnal variation of TEC shows a rapid decay during 1700-2000 hr LT over the three different locations during scintillation days which is observed to be comparatively much less during no scintillation days. The average height of the F-layer in the post-sunset hours over Trivandrum is found to be higher, around 350 km during scintillation days while it is around 260 km during the days on which there is no scintillation activity. The average pre-reversal E xB drift velocity observed around 19:00 hr LT is higher (20 m/s) during scintillation days, whereas during no scintillation days, it is found to be much less (7 m/s). Further, it is observed that the GPS receivers lose their locks whenever the S-4 index exceeds 0.5 (> 10 dB power level) and these loss of lock events are observed to be more around the anomaly crest location (Kolkata). It may be inferred from the present observations that the level of ambient ionization around noon-time, and a fast decay (collapse) of the ionization during afternoon hours followed by rapid increase in the height of the F-layer contributes significantly to the occurrence of scintillations. The present study further indicates that the S-4 index at L-band frequencies increases with an increase in latitude maximizing around the crest of the equatorial ionization anomaly during the post-sunset hours resulting in more loss of lock events in the GPS receiver signals around the EIA crest region. (AU)

• Processo FAPESP: 13/17380-0 - Estudo da ionosfera em baixas latitudes usando ionossondas e GPS.
• Beneficiário: Kavutarapu Venkatesh
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 12/08445-9 - Estudo da variabilidade dia-a-dia da mesosfera, termosfera e ionosfera em baixas latitudes e região equatorial, durante o ciclo solar 24
• Beneficiário: Paulo Roberto Fagundes
• Modalidade de apoio: Auxílio à Pesquisa - Temático