Occurrence of Spread F is more or less a daily phenomenon in the equatorial and low latitudinal stations during high to moderate sunspot number years. In this paper efforts have been made to identify possible precursors of Equatorial Spread F (ESF) using the Total Electron Content (TEC) data of seven GAGAN (GPS Aided Geo Augmented Navigation) stations in India during the two equinoxes of moderate sunspot number year 2004. Large Scale Periodic Structures found prior to TEC bite out can be taken as possible precursors to ESF. A threshold value of the peak to peak amplitude of this wave structure is chosen 2.6 TEC unit above which there is a possibility of ESF or TEC bite out with S4 > 0.26. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.

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University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Advances in Space Research

This paper reports the results of an experiment to identify a possible precursor to equatorial spread F (ESF) with the Giant Meterwave Radio Telescope (GMRT) (latitude: 19.10°N, longitude: 74.05°E geographic; dip: 23°N magnetic) near Pune by simultaneously recording the amplitude and phase of the signal from the radio source 3C218 (RA:09h 15m, Declination: -11 °) at 235, 327, 610, and 1420 MHz in the postsunset-premidnight period 18.5-22.5 LT on 26, 29, and 31 March 2004. Patches of scintillations both in amplitude and phase were observed on 26 and 29 March 2004 at 235, 327, and 610 MHz frequencies starting around 20 LT (LT = UT + 05:00) and extending until 22 LT while the records for 31 March 2004 do not show any scintillations. Significant amplitude scintillations were not observed at 1420 MHz. The most remarkable feature was the presence of large-scale periodic structures in phase prior to onset of amplitude scintillations. The Total Electron Content (TEC) as observed on a GPS link also looking through the same ionospheric volume showed periodic variation of carrier phase prior to onset of scintillations and bite-outs in TEC, which implies that before the onset of ESF, the large-scale wave structures propagate to the height of maximum ionization and beyond. Copyright 2008 by the American Geophysical Union.

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Radio Science

A study of precursors to equatorial spread F using the giant meterwave radio telescope

Geophysical Research Letters

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First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite

Annales Geophysicae

Gravity wave penetration into the thermosphere: sensitivity to solar cycle variations and mean winds

Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx)

Precursors of Equatorial Spread F observing GPS TEC data from different GAGAN stations in India

Journal	Data powered by TypesetAdvances in Space Research
Publisher	Data powered by TypesetElsevier Ltd
ISSN	0273-1177