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Title: Co-ordinated multistation VHF scintillation observations in India during March-April 1991
Authors: Chandra, H
Vyas, G D
Rao, D R K
Pathan, B M
lype, A
Sekaran, B Ram
Naidu, A
Sadique, S M
Salgaonkar, C S
Tyagi, T R
Kumar, P N Vijay
Singh, Lakha
Iyer, K N
Pathak, K N
Gwal, A K
Kumar, Sushil
Singh, R P
Singh, U P
Singh, Birbal
Jain, V K
Navneeth, G N
Koparkar, P V
Rao, P V S Rama
Jaychandran, P T
Sriram, P
Rao, N Y S Santa
Gupta, A Das
Basu, K
Rastogi, R G
Issue Date: Apr-1993
Publisher: NISCAIR-CSIR, India
Abstract: A number of VHF scintillation stations are currently operating in India as part of the All India Co-ordinated Programme of Ionospheric and Thermospheric Studies (AICPITS). The chain covers latitudes right from the magnetic equator to beyond the anomaly crest region. During March-April 1991 co-ordinated observations were made at all the stations of the chain and the data collected analysed jointly. The quarter-hourly values of the occurrence of scintillations along with the start and end times of the patches of scintillations during each night form the data base. Nocturnal variations of the percentage occurrence of scintillations, histograms of percentage occurrence of the number of patches of scintillations during the course of a night and of the patch duration have been computed for each station. Scintillations generally start between 1930and 2000 hrsIST The stations close to the magnetic equator show strong scintillations which last till early morning in a single patch or sometimes with a weakening or absence of scintillations for a short Lime duration. For the stations in the anomaly crest region or beyond, scintillations occur in small patches with periods of no scintillations in between. The nocturnal variations show maximum scintillation activity of about 50 per cent in the equatorial region which drops to about 30 per cent in the anomaly crest region and further reduces to 10 per cent at Delhi, the Northern-most location in the chain. From the latitudinal variations of the percentage occurrence of scintillations, the half width of the equatorial belt of scintillations has been found to vary with local time. It extends right up to Bombay or even beyond it around 2000-2200 hrs but is much narrower after midnight. The occurrence of spread-F during March-April 1991 from ionosonde data at Thumba, Waltair and Ahmedabad representing stations in the equatorial zone, intermediate zone and the anomaly crest zone have been studied. There is a fairly good agreement between the nocturnal variations of spread-F and scintillations.
Page(s): 69-81
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.22(2) [April 1993]

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