Showing papers on "Total electron content published in 1990"
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TL;DR: In this article, the presence or absence of the latitudinal anomaly in TEC on a particular day depended only on the strength of the electrojet current, as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and stations outside the equatorial electrojet.
Abstract: Results are presented on continuous TEC measurements, taken along a chain of stations spaced between 0 deg N and 25 deg N and aligned roughly along the same longitude sector in India, that describe the day-to-day behavior of the location of equatorial anomaly in the TEC during the period of the 1975-1976 sunspot minimum, when the ATS spacecraft was visible from India. It was found that the presence or absence of the latitudinal anomaly in TEC on a particular day depended only on the strength of the electrojet current, as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and stations outside the equatorial electrojet, rather than on the horizontal magnetic field measured only at equatorial stations.
222 citations
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TL;DR: The resolution limit of the image reconstruction process is analyzed in terms of limited‐angle tomography to reconstruct two‐dimensional electron density images of the ionospheric ionosphere.
Abstract: Traditionally, knowledge of the ionospheric electron density is obtained using Faraday rotation or differential Doppler techniques which measure total electron content in columns of the ionosphere. Conventional data processing can only image the electron density in the direction perpendicular to these columns, thereby forming one-dimensional images. Because this data is proportional to line integrals through the region of interest, tomographic techniques may be used to reconstruct two-dimensional electron density images. In this paper, the resolution limit of the image reconstruction process is analyzed in terms of limited-angle tomography.
29 citations
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TL;DR: In this paper, the total electron content along the path to different GPS satellites has been compared using simultaneous integrated phase and incoherent scatter measurements, which allows verification of their technique for determining the ionospheric and tropospheric path delay from the integrated phase data.
12 citations
03 May 1990
TL;DR: In this article, the authors compared GPS and incoherent scatter (IS) measurements of the total electron content (TEC) taken during 1-3 March 1989, and found that the IS profiles are then integrated to produce TEC measurements up to 800 km.
Abstract: GPS and incoherent scatter (IS) measurements of the total electron content (TEC) taken during 1-3 March 1989 are compared. During this period, four different GPS satellites, SV nos. 6, 9, 11, and 12, were observed. The T14100 GPS receiver at Millstone monitored these satellites continuously while they were in view. At the same time, the Millstone UHF radar was sequentially pointed in the direction of several of these satellites taking incoherent scatter measurements. The incoherent scatter measurements produce profiles of the electron density distribution. The IS profiles are then integrated to produce TEC measurements up to 800 km. The combined pseudo-range and phase data of the GPS system measure the group delay at both the L1 (1575.42 MHz) and L2 (1227.6 MHz) frequencies. This information is converted to TEC measurements along the line of sight to the satellite at 19000 km. The comparison of the GPS and incoherent scatter data gives us a new technique for estimating the number of electrons above 800 km. Our results were surprising. The 1-3 March time period was associated with interesting geophysical conditions. The experiment began during quiet geomagnetic conditions and at a time when the daily 10.7 cm solar flux values were moderatemore » (162).« less
7 citations
03 May 1990
TL;DR: In this paper, a first-order estimate of the shape of the electron density profile, Nsube(h), is given by the ratio of the profile's total electron content (TEC) to its peak density (Nmax).
Abstract: : A first-order estimate of the shape of the electron density profile, Nsube(h), is given by the ratio of the profile's total electron content (TEC) to its peak density (Nmax). Applications to transionospheric and hf supported propagation can be aided by models of this quantity, tab and thus the BU/AFGL slab thickness model has been developed to describe the mean variations of slab thickness. In this paper addresses the issue of ;how geomagnetic disturbances affect tab at mid-latitudes, making use of a database of two solar cycles of observations from Hamilton (Ma) and Wallops Island (Va). These results are compared with those deduced from an Italian station pair(Florence and Rome).
3 citations
03 May 1990
TL;DR: In this paper, the latitudinal extent of the equatorial anomaly has been studied using a theoretical model of the ionosphere which incorporates measured values of vertical E x B drift at the earth's magnetic equator.
Abstract: : The latitudinal extent of the equatorial anomaly has been studied using a theoretical model of the ionosphere which incorporates measured values of vertical E x B drift at the earth's magnetic equator. Realistic values of neutral winds are also included. The equatorial anomaly region, typically between plus and minus 20 degrees magnetic latitude, is that part of the world where the highest values of electron density and Total Electron Content, (TEC), normally occur, and hence is very important to high frequency propagation and to trans-ionospheric propagation effects. During the daytime upward E x B drift at the magnetic equator drives the ionization across field lines to higher latitudes, causing crests in ionization to occur at approximately plus and minus 15 deg dip latitude. The latitude range over which the anomaly makes a significant difference in values of foF2 and TEC is calculated as a percent departure from the case with no equatorial electric field. Results from the model studies with different values of realistic electric fields show that the effects of the anomaly can be highly variable and widespread in latitude and local time.
1 citations
03 May 1990
TL;DR: In this article, the background of computerized tomography (CT) and its application to the ionosphere is reviewed, using only total electron content (TEC) data, which can be used to reconstruct a two-dimensional image of the electron density in the Ionosphere.
Abstract: : In this paper the background of computerized tomography (CT) and its application to the ionosphere is reviewed. CT techniques, using only total electron content (TEC) data, can be used to reconstruct a two-dimensional image of the electron density in the ionosphere. The limitations of this technique are discussed and examples showing the limitations and capabilities are presented. Simulation results for two applications are presented: imaging the high latitude trough, and the correction of tracking radar range rate errors. Some possible extensions of the technique are presented.
1 citations