Calendar Item

CalendarVT SuperDARN
TitleSpace@VT Grad Seminar @ Whittemore 457
RecurrenceThis event depends on a recurrence rule
 Event is repeated every Thursday
Starting on Wednesday 14 of September, 2011, ending by Friday 02 of December, 2011.
StartThursday 06 of October, 2011 03:00:00 PM EDT
EndThursday 06 of October, 2011 04:00:00 PM EDT
DescriptionTitle: Mid-latitude ionosphere summer evening anomaly: SuperDARN observations and ray-tracing results

Speaker: Sebastien de Larquier

Abstract: The Super Dual Auroral Radar Network (SuperDARN) provides ionospheric diagnostic information through interpretation of HF propagation in the ionosphere. Typical backscatter is classified into two main sources, Ionospheric Scatter (IS) and Ground Scatter (GS). IS occurs as a result of backscattering on field aligned ionospheric irregularities. GS occurs as a result of backscatter from the terrestrial surface after refraction from the ionosphere. GS is a useful indicator of ionospheric structure as elevation angle and skip distance focusing (shortest range where GS is observed) are a direct result of F region peak height density and width. We use a ray-tracing model coupled with the International Reference Ionosphere (IRI) to simulate realistic propagation conditions at SuperDARN radar sites. Comparison with typical SuperDARN observations shows a very good agreement with model results: this allows the IRI to be used to establish a baseline for quiet time SuperDARN HF radar observations.
A recent study using two years of data from the mid-latitude SuperDARN radar located in Blackstone, Virginia, has revealed an interesting feature in radar observations that could not be understood with classical ionosphere dynamics: an enhancement in GS is observed between April and September around sunset, when the ionosphere is expected to thin out and become almost transparent to HF. SuperDARN observations are compared to data from the Millstone Hill ISR and ray tracing results. This evening anomaly is shown to be related to a prominent density enhancement at F region altitudes observed at Millstone Hill and captured by the IRI. Finally, global results from IRI and the Horizontal Wind Model (HWM07) are presented in relation with previously published satellite observations and proposed mechanisms of the evening enhancement.


Where: Whittemore Hall 457
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