Annual and semiannual TEC effects at low solar activity in midlatitude Atlantic region based on TOPEX

Abstract

The aim of this work is the analysis of the annual and semiannual effects in the total electron content (TEC) of the terrestrial atmosphere during low solar activity. The region of study is the Atlantic Ocean at mid geomagnetic latitudes. Spatial and temporal ionospheric variability are investigated from TOPEX/POSEIDON (T/P) altimetry data. To correct the Earth ionospheric delay on the radar pulse, the satellite's altimeter makes measurements in two channels. The difference between both measurements yields the estimated values of TEC from lower part of the ionosphere up to the height of the satellite. Time series of vertical TEC from T/P, converted on a regular 1 ° x 1 ° grid, are studied making use of Principal Component Analysis. Simulated data from a climatological model of the ionosphere (IRI) are computed to improve our analysis, mainly regarding the data time coverage. The behavior of TEC variations at four different hours of the day are analyzed, highlighting particular characteristics associated with every period (morning, noon, afternoon and night) and with the geomagnetic region. Copyright 2008 by the American Geophysical Union.