The effects of traveling ionospheric disturbances on SuperDARN near range echoes.
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Date
2022
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Abstract
Traveling Ionospheric Disturbances (TIDs) and Near Range Echoes (NREs) are both natural phenomena observed
by SuperDARN High Frequency (HF) radars. This study presents for the first time observations of
NREs in the lower E-region whose amplitudes are moderately modulated by medium-scale TIDs propagating
in the F-region that have been observed by the same radar at another time in the far ranges. Two events during
geomagnetic storms in winter recorded by the SANAE radar and two events during quiet times in summer
recorded by the Zhongshan radar, both radars in the southern hemisphere, are described. The Gradient Drift
Instability (GDI) proved to be the likely mechanism. The GDI is driven by the velocity difference between neutrals
and plasma in the E-region ionosphere, due to the global convection electric field, and can be modulated
by the polarization electric field of a passing TID via the near-vertical equipotential magnetic field lines.
Description
Doctoral Degree. University of KwaZuluNatal, Durban.