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Variability Of Plasma Bubble In The Equatorial Ionosphere At Midnight
There are various types of ionospheric irregularities. Among these is the plasma bubble occurrence. They are most prominent at night time in the equatorial ionosphere. Many of the bubbles drift with approximately the velocity of the background plasma, but it is possible to infer that most bubbles have moved upward at some time in their recent history through the ion composition signals obtained from the Atmospheric Explorer magnetic ion mass spectrometer. The variation of plasma bubble occurrence at midnight round the globe was investigated. The data used covers the period of January to December 1978 which was obtained by observations of the Atmosphere Explorer satellite which passes through the Ionosphere. The total number of satellite passes (trips) during the midnight (i.e. 0000LT) were taken, whether or not they contain bubbles and denote the total number of trips by Tt,, then a count of the number of passes (trips) with bubbles also at midnight (Tb) for each station were taken, and finally a count of the total number of bubbles (B) in all these passes. The regions were divided into three zones namely the Africa sector, the Afro-Asia sector and the Pacific region. The results obtained shows that the number of passes with bubbles (Tb) and the number of bubble occurrence (B) are proportional to each other. It was also observed that the plasma bubble occurrence varies from one region of the world to another at midnight. The highest activity of plasma bubble occurrence (B) was recorded in the African sector; and so also for the number of trips with bubbles (Tb). and followed by the Pacific region. This shows that the Africa sector that was close to the equator has the highest activity of plasma bubble occurrence.
Keywords: plasma bubble, equatorial ionosphere, ion density, ionospheric irregularities, magnetic ions.
Journal of Environmental Extension Vol. 7 2008: pp. 10-15