Measuring and Monitoring Systematic Movements of Equatorial Plasma Bubbles Using Regional GPS TEC Data Maps

Rezy Pradipta and Patricia H. Doherty

Peer Reviewed

Abstract:	In this work, we present a potential application of 2-D regional ?TEC data maps for tracking and monitoring the movements of equatorial plasma bubbles (EPB) across large distances. The 2-D ?TEC data maps had been derived by detrending the absolute GPS TEC values from every individual GPS satellite pass over South America and the Caribbean. In total, data from 200+ GPS receiver stations in South America and the Caribbean had been used in the data analysis/processing. The GPS TEC data detrending was performed numerically using a technique described in Pradipta et al. [2015], which can distinguish TEC depletions (associated with EPB) from wavelike fluctuations in TEC (associated with other types of ionospheric disturbances). The detrended TEC values were then interpolated into a fixed geographic latitude/longitude grid with 0.2 deg x 0.2 deg spatial resolution for data mapping purposes. Several cross-sectional cuts along the zonal direction (i.e. magnetic east-west direction, perpendicular to magnetic meridian) were subsequently extracted from these 2-D ?TEC data maps. An assembly of such crosssectional cuts from a series of sequential ?TEC data maps would show the ?TEC values as a function of time and linear distance along the cut, analogous to a synthesized keogram plot in the analysis of all-sky optical airglow emissions from the upper atmosphere [see e.g. Eather et al., 1976]. The drift movement of equatorial plasma bubbles/depletions can be recognized relatively easily from the overall tilt of the negative-valued portion(s) of the synthesized time-distance ?TEC plot that shows the temporal evolution of the cross-sectional cut. The slope of the tilt in this case directly indicates the zonal drift speed of the equatorial plasma bubbles/depletions. The wide-area coverage of the GPS receiver station network means that more than one bubbles might be captured simultaneously in a single cross-sectional cut. As a result, the zonal drift speed calculation will have to be performed individually for each bubble — thus providing us with several independent drift velocity values. Eastward drift velocities in the range of 50-200 m/s are typical for EPBs observed over South America.
Published in:	Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017) September 25 - 29, 2017 Oregon Convention Center Portland, Oregon
Pages:	3402 - 3408
Cite this article:	Pradipta, Rezy, Doherty, Patricia H., "Measuring and Monitoring Systematic Movements of Equatorial Plasma Bubbles Using Regional GPS TEC Data Maps," Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017), Portland, Oregon, September 2017, pp. 3402-3408. https://doi.org/10.33012/2017.15346
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