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Latitudinal and magnetic flux tube extension of the equatorial spread F irregularities

1983; American Geophysical Union; Volume: 88; Issue: A6 Linguagem: Inglês

10.1029/ja088ia06p04861

2156-2202

M. A. Abdu, R. T. de Medeiros, Yoshiharu Nakamura,

Solar and Space Plasma Dynamics

A comparative study has been carried out of the spread F occurrence characteristics at the magnetic equatorial station, Fortaleza (4°S, 38°W, dip latitude 1.8°S) and the low‐latitude station, Cachoeira Paulista (22°S, 45°W, dip latitude 14°S) located with a relatively small longitudinal difference, in Brazil. The results show strong correlation between the occurrences of spread F events at the two stations for most of the time. While all the spread F events over Cachoeira Paulista are accompained by such events over Fortaleza, the converse is not true. Also, the spread F onset times over the equator are systematically earlier than those over the low latitude. Another interesting result is that while the spread F durations at the two stations are approximately linearly related, an event over Cachoeira Paulista is observed only for those that have durations more than 4–5 hours over Fortaleza. Possible implications of these results on the plasma bubble rise velocities in the equatorial ionosphere are discussed. It seems possible also to predict the approximate duration of a spread F event over the equator by observations carried out at a low‐latitude station situated close to a common magnetic meridional plane.