Vertical ionization drift velocities and range type spread F in the evening equatorial ionosphere

Journal Article · Sat Jan 01 04:00:00 EST 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA088iA01p00399· OSTI ID:6079480

Abdu, M A; de Medeiros, R T; Bittencourt, J A; Batista, I S

Range type spread F indices in the post sunset hours, determined from ionograms, are compared with F layer vertical velocities, also deduced from ionograms, for a period of one year, over the magnetic equatorial station Fortaleza (geographic coordinates: 4/sup 0/S, 38/sup 0/W; dip latitude: 1.8/sup 0/S), Brazil. Besides good correlation between the two parameters, the results suggest the presence of a certain threshold value for the vertical ionization velocity and a corresponding threshold height for the base of the evening F layer, as one of the necessary conditions for the occurrence of spread F irregularities valid for southern solstice (summer) and equinoctial months. The nature of the possible variabilities in the amplitude of the initial perturbation in the ionization (seeding mechanism), which is another prerequisite for the generation of irregularities, is discussed briefly.

• Research Organization: Instituto de Pesquisas Espaciais-INPE, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico-CNPq, 12200 So Jose dos Campos, Sao Paulo, Brazil
• OSTI ID: 6079480
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 88:A1; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
EARTH ATMOSPHERE
F REGION
GEOMAGNETIC EQUATOR
ION DENSITY
ION DRIFT
IONOSPHERE
IONOSPHERIC STORMS
PLANETARY IONOSPHERES
SEASONAL VARIATIONS
VARIATIONS