Abstract
Abstract. Multistation observations of ionosphere scintillation at VHF (250 MHz) and GNSS L1 frequency from three locations – (i) Bokkhali (BOK) (geographic 21.6° N, 88.2° E, dip 31.48°, (ii) Raja Peary Mohan College Centre (RPMC) (geographic 22.66° N, 88.4° E, dip 33.5°) and (iii) Krishnath College Centre (KNC), Berhampore (geographic 24.1° N, 88.3° E, dip 35.9°) – at ~ 1° latitudinal separations near the northern crest of the equatorial ionization anomaly (EIA) of the Indian longitude sector are investigated in conjunction with total electron content (TEC) data and available ionosonde data near the magnetic equator to study fine structure in spatial and temporal variability patterns of scintillation occurrences. The observations are carried out in the autumnal equinoctial months of a high solar activity year (2011). In spite of smaller latitudinal/spatial separation among the observing stations, conspicuous differences are reflected in the onset time, duration, fade rate and fade depth of VHF scintillations as well as in spectral features. Scintillations are mostly associated with depletion in TEC around the anomaly crest and occurrence of ESF near the magnetic equator at an earlier time. Not only the strength of EIA, but also the locations of observing stations with respect to the post-sunset resurgence peak of EIA seem to play dominant role in dictating the severity of scintillation activity. A secondary enhancement in diurnal TEC in the post-sunset period seems to accentuate the irregularity activities near the anomaly crest, and a threshold value of the same may fruitfully be utilized for the prediction of scintillation around the locations. An idea regarding latitudinal extent of scintillation is developed by considering observations at L1 frequency from the GPS and GLONASS constellation of satellites. A critical value of h'F near the magnetic equator for the occurrence of simultaneous scintillation at the three centres is suggested. The observations are discussed considering electrodynamical aspect of equatorial irregularities.
Highlights
General features of scintillation variabilityMultistation ionospheric scintillation observations for the period 1 September to 15 November 2011 of the autumnal equinoctial months of the high solar activity year have been analyzed under present investigations
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Intense scintillations with fast fading rate plague the region over the anomaly crest; comparatively lesser fade depth and fade rate characterize the region beyond the same
Summary
Multistation ionospheric scintillation observations for the period 1 September to 15 November 2011 of the autumnal equinoctial months of the high solar activity year have been analyzed under present investigations. In the post-sunset hours intense amplitude scintillations are recorded at VHF frequency with percentage occurrence of scintillation at about 55 % and 50 % of observing period at RPMC and KNC, respectively. In the developed phase of post-sunset scintillation, much lower values of decorrelation time, especially for BOK and RPMC, in the range ≈ 0.07–1.2 s, are estimated, whereas at KNC the same is a little higher at ≈ 0.17–1.5 s, indicating a decreased rate of peak-to-peak variation at KNC compared to BOK and RPMC. For postmidnight hours all the three centres register higher values of decorrelation time, which lie in the range of ≈ 1.5–3.5 s at KNC, while BOK and RPMC recorded comparatively lower decorrelation time than KNC, ranging between 1.0–3.0, indicating diminished rate of peak-to-peak signal fluctuations. It is clear from above that all the fine structure parameters such as onset time, duration, fade depth, fade rates, decorrelation time etc. are notably different for the three centres in spite of the fact that the stations are located in a close vicinity to each other
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