TEC

About: TEC is a research topic. Over the lifetime, 5119 publications have been published within this topic receiving 84696 citations.

Latitude dependence of ionosphere total electron content: Observations during sudden commencement storms

Abstract: The latitude dependence of the changes in the ionosphere total electron content (TEC) has been studied during 12 magnetic storms. TEC observations were obtained at Hamilton, Massachusetts, and Arecibo, Puerto Rico. Definite latitude differences are observed in the TEC responses during the magnetic storms: both TEC enhancements and TEC depletions are observed at Hamilton, while only enhancements are measured at Arecibo. A pre-local midnight TEC ‘ledge’ is frequently observed in the Arecibo storm data but is seldom observed in the higher-latitude Hamilton data. These enhanced ledges in the Arecibo TEC, together with the nighttime TEC depletions measured at Hamilton, produce large south-to-north differences in the ionosphere TEC. The ledges at Arecibo may arise from electrodynamic drift effects associated with westward electric fields; the role of the motion term in the continuity equation for the TEC is assessed under these conditions. The local evening enhancements in the TEC during certain large storms are discussed in the context of the latitude dependence of the storm time magnetic field variations measured from Great Whale River to San Juan. It is shown that the large TEC enhancements appear to be associated with large positive geomagnetic bays at middle to high latitudes.

Latitudinal variations of nighttime enhancements in total electron content

Abstract: Latitudinal variations of the various characteristics of nighttime anomalous enhancements in total electron content (TEC) are presented by considering TEC data from the ATS series of satellites for a 2-month period from a number of stations in the northern hemisphere extending from 2° to 63° dip latitude. The latitudinal variations of the various TEC enhancement characteristics are found to be strikingly similar, and they reveal a pattern of cyclic variation with two distinct minima, one at 30°N and the other at 60°N (dip latitude). The TEC enhancements show a strong positive correlation with geomagnetic activity at middle and high latitudes and no significant correlation at low latitudes. The observed pattern of the latitudinal vaiations of the TEC enhancements is discussed in the light of the potential source mechanisms.

Observations and simulations of quasiperiodic ionospheric oscillations and large‐scale traveling ionospheric disturbances during the December 2006 geomagnetic storm

Abstract: [1] A numerical simulation was performed to investigate quasiperiodic ionospheric oscillations that were observed with periods of 4–5 h by the ionosonde network (Okinawa, Yamagawa, Kokubunji, and Wakkanai) in Japan during the 15 December 2006 magnetic storm. This simulation used the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) 2.0 model. The CMIT model reproduced the main characteristics of the observed ionospheric oscillations, although it remains a challenging task to simulate the observations in a quantitative sense. Term analysis of the ion continuity equation demonstrated that the ionospheric oscillations in this event were mainly induced by the disturbed neutral winds, which were associated with the large scale thermospheric circulation and traveling atmospheric disturbances (TADs) during the storm. The TADs simulated from the model were then compared with those observed by the GPS Earth Observation Network (GEONET) in Japan to validate the simulation results. A prominent northward propagating large-scale traveling ionospheric disturbance (LSTID) during daytime, seen by the GEONET total electron content (TEC) data, was captured by the CMIT model. Two southward LSTIDs observed by GEONET GPS network were also reproduced by the CMIT model. However, the model gave faster phase speeds for the southward propagating LSTID occurred during 0620–0800 UT and the northward propagating LSTID; furthermore, the model missed the LSTID seen in the TEC perturbation data during 0140–0220 UT. Finally, both observations and simulations showed a strong hemispheric asymmetry for the TAD propagation that occurred during 0000–0400 UT, which may be associated with the hemispheric asymmetry of the change of Joule heating at high latitude.

An Evaluation of Interpolation Techniques for Reconstructing Ionospheric TEC Maps

Abstract: Maps of the total electron content (TEC) of the ionosphere can be reconstructed using data extracted from global positioning system (GPS) signals. For historic and other sparse data sets, the reconstruction of TEC images is often performed using a multivariate interpolation technique. Although there are many interpolation methods available, only a limited number, for example kriging, have been applied to TEC data. This paper presents a quantitative comparison of various commonly used algorithms for scattered-data interpolation over a range of sparsi- ties. Techniques evaluated include a relatively new approach called Adaptive Normalized Convolution (ANC) that has not previously been applied to ionospheric reconstruction. The proposed evaluation scheme employs a quantitative methodology applied to both simulated and real TEC data. Results show that, although the performance of kriging is good in many cases, it is several times worse than the best performing techniques at some sparsities. Natural-neighbor interpolation has a better overall performance than kriging for both simulated and TEC data. Although its performance is a few percent worse than other methods for the simulated data, ANC produces the best performance for the TEC reconstructions.