Browsing by Author "Doherty, Patricia H."
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Item Restricted An effective TEC data detrending method for the study of equatorial plasma bubbles and traveling ionospheric disturbances(American Geophysical Union, 2015-11-18) Pradipta, Rezy; Valladares, Cesar E.; Doherty, Patricia H.Using a mechanical analogy of rolling a cylindrical barrel on a rough uneven surface, we developed a special method for detrending the GPS‐derived total electron content (TEC) data. This method is specifically designed to recognize the presence of depletions in the TEC time series data and handle them differently from wavelike features. We also demonstrate a potential application of this technique to map the detailed geographic profile of TEC depletions over the equatorial region, using the South American sector as an example.Item Restricted Interhemispheric propagation and interactions of auroral traveling ionospheric disturbances near the equator(American Geophysical Union, 2016-02-11) Pradipta, Rezy; Valladares, Cesar E.; Carter, Brett A.; Doherty, Patricia H.We present the results of our GPS total electron content and ionosonde observations of large‐scale traveling ionospheric disturbances (LSTIDs) during the 26 September 2011 geomagnetic storm. We analyzed the propagation characteristics of these LSTIDs from the auroral zones all the way to the equatorial region and studied how the auroral LSTIDs from opposite hemispheres interact/interfere near the geomagnetic equator. We found an overall propagation speed of ∼700 m/s for these LSTIDs and that the resultant amplitude of the LSTID interference pattern actually far exceeded the sum of individual amplitudes of the incoming LSTIDs from the immediate vicinity of the interference zone. We suspect that this peculiar intensification of auroral LSTIDs around the geomagnetic equator is facilitated by the significantly higher ceiling/canopy of the ionospheric plasma layer there. Normally, acoustic‐gravity waves (AGWs) that leak upward (and thus increase in amplitude) would find a negligible level of plasma density at the topside ionosphere. However, the tip of the equatorial fountain at the geomagnetic equator constitutes a significant amount of plasma at a topside‐equivalent altitude. The combination of increased AGW amplitudes and a higher plasma density at such altitude would therefore result in higher‐amplitude LSTIDs in this particular region, as demonstrated in our observations and analysis.Item Restricted Ionosonde observations of ionospheric disturbances due to the 15 February 2013 Chelyabinsk meteor explosion(American Geophysical Union, 2015-10-29) Pradipta, Rezy; Valladares, Cesar E.; Doherty, Patricia H.We report the results of our investigations on the potential ionospheric effects caused by the 15 February 2013 Chelyabinsk meteor explosion. We used the data from a number of digisonde stations located in Europe and Russia to detect the traveling ionospheric disturbances (TIDs) likely to have been caused by the meteor explosion. We found that certain characteristic signatures of the TIDs can be identified in individual ionogram records, mostly in the form of Y‐forking/splitting of the ionogram traces. Based on the arrival times of the disturbances, we have inferred the overall propagation speed of the TIDs from Chelyabinsk to be 171 ± 14 m/s.