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Found 7 entries in the Bibliography.

Showing entries from 1 through 7

2012

Longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics

Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian \~37\textdegreeE and 290\textdegreeE, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation, such as from VEFI onboard Communication/Navigation Outage Forecasting System (C/NOFS) satellite and JULIA radar, is equally promising. The observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences; especially the equatorial anomaly peaks expand to higher latitudes more in American sector than the African sector, indicating that the vertical drift in the American sector is stronger than the African sector.

Yizengaw, E.; Zesta, E.; Moldwin, M.; Damtie, B.; Mebrahtu, A.; Valladares, C.; Pfaff, R.;

Published by: Journal of Geophysical Research Published on: 07/2012

YEAR: 2012 DOI: 10.1029/2011JA017454

Tomography; vertical drift

2010

The November 2004 superstorm: Comparison of low-latitude TEC observations with LLIONS model results

Hei, Matthew; Valladares, Cesar;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-03-2010

YEAR: 2010 DOI: 10.1016/j.jastp.2009.03.025

2006

Extreme longitudinal variability of plasma structuring in the equatorial ionosphere on a magnetically quiet equinoctial day

McDonald, Sarah; Basu, Sunanda; Basu, Santimay; Groves, Keith; Valladares, Cesar; Scherliess, Ludger; Thompson, Donald; Schunk, Robert; Sojka, Jan; Zhu, Lie;