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A study of equatorial spread-F
Journal of Atmospheric and Terrestrial Physics, 1963Data from seven stations ranging in magnetic dip from 0° to 44°N have been analysed to study night time and seasonal variations of spread-F through nearly half a solar cycle. It is observed that the inhibition of spread-F due to geomagnetic activity is maximum in the equinoxes.
S. Rangaswamy, K.B. Kapasi
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Geomorphology of spread F and characteristics of equatorial spread F
Journal of Geophysical Research, 1959Between magnetic latitudes 20°N and 20°S there is a well defined region where spread F is a normal occurrence on magnetically quiet days. Equatorial spread F is a night-time phenomenon that begins between 1900 and 2200 by a characteristic doubling of the layer and an increase in virtual height, indicating a vertical velocity.
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Duration of equatorial spread F
Nature, 1975IT is well established1–3 that the spread-F phenomenon, which is observed as diffuse echoes on the ionograms is a common feature during night time between the dip latitudes 20°N and 20°S. Based on the study of ionograms and published monthly f0F2 bulletins, morphological features of spread F have been reported for several equatorial stations1,4–10 ...
V. V. SOMAYAJULU +2 more
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Journal of Atmospheric and Terrestrial Physics, 1970
Abstract Spread- F echoes are not due to partial reflection from small irregularities. Rather they are due to total reflection from large tilted surfaces of ionization. The geometry of these surfaces is examined using ionograms and airglow observations, together with Australian experiments reported in the literature.
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Abstract Spread- F echoes are not due to partial reflection from small irregularities. Rather they are due to total reflection from large tilted surfaces of ionization. The geometry of these surfaces is examined using ionograms and airglow observations, together with Australian experiments reported in the literature.
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Journal of Atmospheric and Terrestrial Physics, 1963
An explanation of the position of the spread-F equator under sunspot maximum and sunspot minimum conditions is put forward. This explanation is based on the theory of spread-F irregularity production by Martyn amplification of irregularities initiated by hydromagnetic waves.
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An explanation of the position of the spread-F equator under sunspot maximum and sunspot minimum conditions is put forward. This explanation is based on the theory of spread-F irregularity production by Martyn amplification of irregularities initiated by hydromagnetic waves.
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AIP Conference Proceedings, 1992
Because of its complex nature, the knowledge of spread F is not commensurate with the long period of its study. Rockets, satellites and radar systems have greatley advanced observational information on spread F. We have outlined some of these observations and presented information on certain morphology and characteristics of both the equatorial and ...
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Because of its complex nature, the knowledge of spread F is not commensurate with the long period of its study. Rockets, satellites and radar systems have greatley advanced observational information on spread F. We have outlined some of these observations and presented information on certain morphology and characteristics of both the equatorial and ...
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Journal of Atmospheric and Terrestrial Physics, 1981
Our understanding of equatorial spread-F (ESF) phenomena has progressed significantly in the past several years. ESF phenomena involves ionospheric irregularities spanning some 5–6 orders of magnitude in scale size. The largest scale sizes, on the order of many kilometers, are thought to be caused by a plasma fluid type Rayleigh-Taylor instability ...
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Our understanding of equatorial spread-F (ESF) phenomena has progressed significantly in the past several years. ESF phenomena involves ionospheric irregularities spanning some 5–6 orders of magnitude in scale size. The largest scale sizes, on the order of many kilometers, are thought to be caused by a plasma fluid type Rayleigh-Taylor instability ...
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Mid-latitude spread-F structure
Journal of Atmospheric and Terrestrial Physics, 1988Spread-F has been observed at frequencies of 1.98, 3.84 and 5.80 MHz and multiple angles of arrival have been resolved using an HF radar near Brisbane (27°S, 153°E). The spreading of the ionogram trace has been shown to be due to a spread in angles of arrival of echoes, rather than any 'vertical' spreading.
From W.R., Meehan D.H.
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Classification of spread-F ionograms
Journal of Atmospheric and Terrestrial Physics, 1962Abstract Scaling of original ionograms obtained in the polar regions has lead to a classification scheme for spread-F ionograms. Defined are three types of frequency spreading (spreadish-F, furcated-F and spurred-F) and one type of range spreading. Each type is subdivided into species.
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A study of midlatitude spread-F
Journal of Atmospheric and Terrestrial Physics, 1977Abstract Results of a study of the occurrence of spread-F at Christchurch (43.6°S, 172.8°E; invariant latitude Λ = 49.0°S) over the period June 1965-December 1974 are presented. There is a significant positive correlation between the occurrence of spread-F in the post-midnight period and Kp, the occurrence of spread-F lagging behind Kp by 1 to 2 days.
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