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Ann. Geophys., 24, 1419-1427, 2006
www.ann-geophys.net/24/1419/2006/
© European Geosciences Union 2006
Simultaneous radar and spaced receiver VHF scintillation observations of ESF irregularities
D. Tiwari1, B. Engavale1, A. Bhattacharyya1, C. V. Devasia2, T. K. Pant2, and R. Sridharan2
1Indian Institute of Geomagnetism, Plot No. 5, Sector-18, New Panvel (W) New Mumbai- 410218, India
2Space Physics Laboratory, Vikram Sarabhai Space Centre Thiruvananthapuram-695022, India
Abstract. Simultaneous observations of equatorial spread F (ESF) irregularities made
on 10 nights during March-April 1998 and 1999, using an 18-MHz radar at
Trivandrum (77° E, 8.5° N, dip 0.5° N) and two spaced
receivers recording scintillations on a 251-MHz signal at Tirunelveli
(77.8° E, 8.7° N, dip 0.4° N), have been used to study
the evolution of Equatorial Spread F (ESF) irregularities. Case studies have
been carried out on the day-to-day variability in ESF structure and dynamics,
as observed by 18-MHz radar, and with spaced receiver measurements of
average zonal drift Vo of the 251-MHz radio wave diffraction
pattern on the ground, random velocity Vc, which is a measure
of random changes in the characteristics of scintillation-producing
irregularities, and maximum cross-correlation CI of the spaced
receivers signals. Results show that in the initial phase of plasma bubble
development, the greater the maximum height of ESF irregularities responsible
for the radar backscatter, the greater the decorrelation is of the spaced
receiver scintillation signals, indicating greater turbulence. The relationship
of the maximum spectral width derived from the radar observations and
CI also supports this result.
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