Results 261 to 270 of about 12,217,136 (305)

A study of midlatitude spread-F

Journal of Atmospheric and Terrestrial Physics, 1977
Abstract 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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Mid-latitude spread-F structure

Journal of Atmospheric and Terrestrial Physics, 1988
Spread-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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Spread-F and the Latitude Variation of Occurrence of Whistlers

Nature, 1961
RECENT work of whistling atmospherics has suggested that the incidence of the phenomenon is dependent on latitude. Crouchley1, using data from Australian and Japanese stations, demonstrated that whistler activity reaches a maximum at about 45°geomagnetic latitude, while the Stanford group 2 report a maximum of occurrence at 50°geomagnetic latitude.
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The nocturnal and seasonal variations of spread-F

Journal of Atmospheric and Terrestrial Physics, 1963
Abstract The nocturnal variations of spread- F at Waltair using data over a period of 22 months (March, 1960–December, 1961) are studied and discussed in comparison with the variations at other equatorial stations. The seasonal characteristics of spread- F are studied separately for magnetically quiet and disturbed days, using data at four ...
B.V. Krishnamurthy, B.Ramachandra Rao
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On spread-F in the ionosphere before earthquakes

Journal of Atmospheric and Solar-Terrestrial Physics, 2006
Occurrence probability of the ionospheric spread-F in connection with earthquakes is analyzed. The F-layer is not close to the Earth (∼400 km), but in situ data could be obtained either by ionospheric sounders or by satellites. Data from the two Japanese ionospheric stations Kokubunji and Akita have been analyzed to find out long-term (a few weeks ...
Liperovskaya, E. V., Liperovsky, V. A., Silina, A. S., Parrot, Michel   +3 more
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Equatorial Spread-F and Magnetic Activity

Nature, 1958
IT is well known that the ionospheric spread-F condition is extremely common at night in equatorial regions. At Ibadan, Nigeria (latitude 7½°N.), this has been especially so during the past 2½ years of high sunspot activity. It is believed that the same irregularities which produce the wide spread of scattered echoes from the F-region are also ...
A. J. LYON, N. J. SKINNER, R. W. WRIGHT
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Control of equatorial spread-F by the F-layer height

Journal of Atmospheric and Terrestrial Physics, 1966
Abstract The dependence of equatorial spread-F occurrence on the height of the layer is examined in detail in the case of two equatorial stations viz. Kodaikanal and Huancayo, lying close to the magnetic equator. The percentage of occurrence associated with different heights is found to vary with time, season and longitude.
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Spread F modeling over Brazil

Journal of Atmospheric and Solar-Terrestrial Physics, 2017
Abstract Based on a numerical model developed by Carrasco et al. (2014), the dynamics and morphology of ionospheric plasma bubbles for both magnetic hemispheres over Brazil are examined. Observational results show that the post sunset maximum velocity of the pre-reversal vertical drift velocity, V P , has different values at the conjugate ...
A.J. Carrasco, I.S. Batista, J.H.A. Sobral, M.A. Abdu   +3 more
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Spread-F at Temperate and High Latitudes

IETE Journal of Research, 1966
ABSTRACTSpread-F at temperate and high latitudes has been analysed to study its variation with season, geomagnetic activity, sunspot activity and h'F. It is observed that at low temperate latitudes there is no correlation with geomagnetic activity. At high temperate latitudes spread-F is positively correlated with geomagnetic activity in winter and ...
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Spread-F and the parameters of the F-layer of the ionosphere-II. Spread-F and F-layer height

1962
An analysis has been made of spread-F data obtained from I.G.Y. f{hook}-plots for several ionosonde stations grouped about longitude 75°W to establish whether there is any connexion between the incidence of the frequency-spreading component of spread-F and the height of the F2-layer.
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