Bittencourt, J.A. Fundamentals of plasma physics 1 J.A. Bittencourt.-3rd ed. p. cm. Includes index. 978-1-4419-1930-4 ISBN 978-1-4757-4030-1 (eBook) ISBN

We have carried out a comparative study of the evening prereversal enhancements in the equatorial F region vertical ionization drift velocities (V z) over Fortaleza (4øS, 38øW), Brazil, and Jicamarca (12øS, 77øW), Peru, two magnetic equatorial stations in the American zone. The results show profound dissimilari.ties in the seasonal trends in the times and widths of the V prereversal peak, which reflect in the sprea• F characteristics as well, at the two stations. The dissimilarities are shown to be arising mainly from the difference in the magnetic field declination angles that causes differences in the conjugate E region sunset durations and, hence, in the F region polarization electric field development rates at the two stations.

Longitudinal and seasonal asymmetries in the evening ionospheric F region plasma vertical drift (V z) enhancements, between two longitudinally separated stations situated along the magnetic equator, in the American sector, are investigated under solar maximum conditions, based on results obtained from the analysis of ionosonde data for these stations. The two stations are Huancayo, Peru, and Fortaleza, Brazil, which have markedly different magnetic declination angles. The observed asymmetries are interpreted using a detailed numerical simulation of the E and F region electrodynamic coupling process that takes into account also its asymmetry about the magnetic equator arising from the finite magnetic declination angle. The results of the simulation show, in agreement with observations, that the occurrence time of the evening F region vertical drift prereversal peak and its seasonal variation at a station are controlled by the magnetic declination angle at that station, which determines the seasonal variation of the sunset times (and hence the integrated Pedersen conductivity longitudinal gradient) at its magnetic conjugate E layers. The amplitude of the prereversal peak, on the other hand, undergoes the influence of the magnetic declination angle as well as of the thermospheric zonal wind component. 12,055

A theoretical analysis of the time dependent distribution of ionization in the low‐latitude ionosphere is performed by using a realistic dynamic computer model of the equatorial F region, with special interest in the vertical motions of the electron density profile at the magnetic equator. The time dependence of the F2 peak height, at the magnetic equator, is governed primarily by the electromagnetic plasma drift velocity. It is shown that, for special time periods during sunset and evening hours, when the height of the F layer is above a threshold of 300 km, the apparent vertical displacement velocity of the F layer, inferred from ionosonde measurements, is the same as the vertical plasma drift velocity, as determined from incoherent backscatter radar measurements in the F region.

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