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Diurnal Transport Effects on the F-Region Plasma at Chatanika Under Quiet and Disturbed Conditions

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Planetary and Space Science





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The predictions of a time-dependent, three-dimensional model of the high-latitude ionosphere have been compared with the diurnal variations of plasma convection velocities and electron densities observed at Chatanika on geomagnetically quiet and disturbed days near equinox. The model predictions for the quiet day are in good agreement, both qualitatively and quantitatively, with the measurements. The model predictions for the disturbed day are in qualitative agreement with the measurements, but at certain local times there are significant quantitative differences. Also, the model cannot produce the detailed fine structure in the electron density that was observed on the disturbed day owing to the lack of fine structure in the model convection pattern and auroral precipitation fluxes. For the quiet day, the gross features of plasma convection are consistent with a symmetric two-cell pattern with a cross-polar cap potential of 52 kV. For the disturbed day, on the other hand, the observed plasma convection is consistent with an asymmetric two-cell pattern with enhanced plasma flow in the dusk sector and a cross-polar cap potential of 90 kV. For both the quiet and disturbed days, the lower latitude region of the high-latitude ionosphere was found to be sensitive to the competition between the vertical components of the electrodynamic and wind-induced ion drifts. For both days, horizontal plasma transport was found to be very important. One consequence of transport is that on the dayside the peak density at a given altitude occurs at a later local time as altitude increases. Another consequence of transport is that high electron densities are maintained in regions devoid of ionization sources, particularly on the disturbed day.


Originally published by Elsevier. Publisher’s PDF available through remote link.