Bibliography

Comparisons of foF2 with IRI model and equatorial vertical drifts

Measurements of the critical frequency, foF2 recorded over Ibadan: 7.4°N, 3.9°E (geographic), 6°S (dip angle) have been compared with the International Reference Ionosphere (IRI-2007) model for solar maximum geomagnetically quiet conditions, with a view to determining what modifications might bring about better predictions for the model. Our results reveal that the present version of IRI essentially reproduces diurnal trends and the general features of the experimental observations for all seasons, except for nighttime June solstice periods, which the model seriously overestimated. The model errors ranging from 50\% to 125\% over the four seasons considered in this study. It is also indicated that the percentage relative deviations between the observed and the modeled values vary approximately from −11\% to 12\% (March), −34\% to 11\% (June), −16\% to 12\% (September), and −10\% to 13\% (December). An unexpected feature of foF2 is obvious and remarkable reduction in values during nighttime June solstice periods compared to that in other seasons. Relationship between equatorial vertical drift and foF2 is also investigated. However, cross correlation analysis reveals strong anti-correlation between vertical drift and critical frequency during the daytime hours, but exceptionally opposite is the case for the nighttime sector. The discrepancies which are noted, particularly during June solstice season are attributed to processes most likely within the thermosphere and from meteorological influences during quiet magnetic conditions.

Oyekola, O.S.;

Published by: Advances in Space Research      Published on:

YEAR: 2011     DOI: https://doi.org/10.1016/j.asr.2011.06.027

foF2; IRI-model; Equatorial-ionosphere; Ion drift; High solar activity

Spatial and temporal ion drift variability in the high -latitude F region during southward IMF

The purpose of the following research is to investigate the role and contribution of variability or structure in the ion drift to the overall Joule heating rate during times of southward interplanetary magnetic field (IMF). This investigation is limited to southward IMF because the convection patterns are generally more stable and reproducible than those seen for a northward IMF. This allows us to organize the data according to features of the convection pattern and thus produce results that can be used in model simulations of the ionosphere-thermosphere. The contribution of variability or structure in the ion drift to the overall Joule heating is organized into two parts. The first part focuses on the characteristic spatial structure in the ion drift in the F-region ionosphere and how it relates to the bulk ion flow, the large-scale spatial gradient in the bulk ion flow, and the ion temperature. We consider separately the polar cap and auroral zone during the summer and the winter at dawn and dusk during times of steady southward IMF. The second part of this investigation examines the spatial and temporal variability in the ion drift and its contribution to the total Joule heating rate in the F-region ionosphere in the summer and the winter at all magnetic local times (MLT) that are sampled by our data set. This second investigation includes more data than the first investigation by relaxing the stability conditions for southward IMF as well as allowing weaker southward IMF. These topics are investigated utilizing data from the Dynamics Explorer 2 (DE-2) satellite.

Johnson, Eric;

Published by: ProQuest Dissertations and Theses      Published on:

YEAR: 2005     DOI:

Pure sciences; F region; High-latitude; interplanetary magnetic field; Ion drift; atmosphere; 0725:Atmospheric sciences