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TEC

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


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Journal ArticleDOI
TL;DR: In this article, a combination of ground-based Global Positioning System (GPS) total electron content (TEC), and the meridian chain of ionosondes distributed along the Latin America longitude of ~280° E was used to investigate positive ionospheric storm effects.
Abstract: . Positive ionospheric storm effects that occurred during the superstorm on 20 November 2003 are investigated using a combination of ground-based Global Positioning System (GPS) total electron content (TEC), and the meridian chain of ionosondes distributed along the Latin America longitude of ~280° E. Both the ground-based GPS TEC and ionosonde electron density profile data reveal significant enhancements at mid-low latitudes over the 280° E region during the main phase of the November 2003 superstorm. The maximum enhancement of the topside ionospheric electron content is 3.2–7.7 times of the bottomside ionosphere at the locations of the ionosondes distributed around the mid- and low latitudes. Moreover, the height of maximum electron density exceeds 400 km and increases by 100 km compared with the quiet day over the South American area from middle to low latitudes, which might have resulted from a continuous eastward penetration electric field and storm-generated equatorward winds. Our results do not support the conclusions of Yizengaw et al. (2006), who suggested that the observed positive storm over the South American sector was mainly the consequence of the changes of the bottomside ionosphere. The so-called "unusual" responses of the topside ionosphere for the November 2003 storm in Yizengaw et al. (2006) are likely associated with the erroneous usage of magnetometer and incomplete data.

30 citations

Journal ArticleDOI
TL;DR: The plasticizer content in the film coating influenced the dissolution profile of theophylline from pellets coated with Eudragit S100:L100 (1:1) and a TEC level of approximately 30% in the films was the critical amount for initiating drug release during dissolution testing at pH 6.0.

30 citations

Journal ArticleDOI
TL;DR: In this article, the authors have analyzed 15 months of data for the period between 01 September, 2006 and 30 November, 2007 statistically, and found that anomalous depletions and enhancements occurred in the light of magnetic storms and earthquakes.
Abstract: Employing a GPS receiver we have monitored ionospheric total electron content (TEC) at Agra (Geographic Lat. 27.2°N, Long. 78°E), India since 24 June, 2006. In this paper we have analysed 15 months of data for the period between 01 September, 2006 and 30 November, 2007 statistically. The results show anomalous depletions and enhancements which are examined in the light of magnetic storms and earthquakes. As magnetic conditions have remained quiet throughout the period of data except some sporadic cases, majority of the TEC anomalies are interpreted as due to earthquakes. We find that out of 43 cases of moderate and high magnitude earthquakes (M ⩾ 5.0) there are 23 cases in which both depletions and enhancements occurred and in the remaining 17 cases (no data available in three cases) either of enhancement or depletion occurred. In general the anomalies occurred 0–9 days before the earthquakes as precursors. The correlation coefficient of 0.8 is found between the two sets of data which satisfy null hypothesis. A mechanism responsible for TEC anomalies under the influence of earthquakes is discussed also.

30 citations

Journal ArticleDOI
TL;DR: In this article, the authors used TEC data from a BeiDou geostationary orbit (GEO) receiver network to observe and investigate ionospheric longitudinal variations within the zonal scale of 1000 km over Central China (112°-122°E, 27°-31°N; 20°-24°N magnetic latitudes) during June 2015 - December 2016.
Abstract: Many studies have devoted to the longitudinal variations of the ionosphere globally. However, the ionospheric longitudinal variations in a small region are rarely reported. In this paper, we for the first time use TEC data from a BeiDou geostationary orbit (GEO) receiver network to observe and investigate ionospheric longitudinal variations within the zonal scale of 1000 km over Central China (112°-122°E, 27°-31°N; 20°-24°N magnetic latitudes) during June 2015 - December 2016. The BeiDou GEO TEC provides a good dataset to study longitudinal variations, compared with Non-GEO TEC, without contaminating the spatial variations and elevation changes due to satellite motion. Pronounced daytime longitudinal gradients within the distance of 1000 km are present in BeiDou GEO TEC. It was found that the TEC is generally larger in the west than in the east. In some cases, the TEC gradient magnitude is larger than 45 TECU. For most events, the obvious daytime longitudinal gradients are accompanied by the TEC enhancement. The occurrence rate of daytime longitudinal gradients under different geomagnetic activities is similar, whereas strong daytime longitudinal gradients mainly occur under the moderate and strong disturbance geomagnetic activities. These observations suggest that the electric field disturbances could have significant effects on producing the observed ionospheric longitudinal gradients.

30 citations

Journal ArticleDOI
TL;DR: In this paper, the main characteristics of night-time enhancements in TEC during magnetic storms are compared with those during quiet nights for different seasons and solar activity conditions at Palehua, a low latitude station during the period 1980-1989.
Abstract: . The main characteristics of night-time enhancements in TEC during magnetic storms are compared with those during quiet nights for different seasons and solar activity conditions at Palehua, a low latitude station during the period 1980–1989. We find that the mean amplitude has both a seasonal and solar activity dependence: in winter, the values are higher for weak storms as compared to those during quiet nights and increase with an increase in solar activity. In summer, the mean amplitude values during weak storms and quiet nights are almost equal. But during equinox, the mean amplitude values for quiet nights are greater than those during weak storms. The mean half-amplitude duration is higher during weak storms as compared to that during quiet nights in summer. However, during winter and equinox, the durations are almost equal for both quiet and weak storm nights. For the mean half-amplitude duration, the quiet night values for all the seasons and equinoctial weak storm values increase with an increase in solar activity. The occurrence frequency (in percent) of TEC enhancement during weak storms is greater than during quiet nights for all seasons. The mean amplitude, the mean half-amplitude duration and the occurrence frequency (in percent) of TEC enhancement values are higher during major storms as compared to those during quiet nights. The above parameters have their highest values during pre-midnight hours. From the data analysed, this behaviour is true in the case of major storms also. Key words. Ionosphere (ionospheric disturbances; plasma convection) Magnetospheric physics (storms and substorms)

30 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023303
2022578
2021284
2020321
2019293
2018272