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Total electron content

About: Total electron content is a research topic. Over the lifetime, 3999 publications have been published within this topic receiving 73935 citations.


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TL;DR: In this article, the ionospheric effects of a halo coronal mass ejection (CME) initiated on the Sun on September 20, 1999, and causing the largest magnetic storm during this month on September 22, 23, and 24, 1999 were studied through their effects on a prototype of a Global Positioning System (GPS)-based navigation system called Wide Area Augmentation System (WAAS) and their impact on global VHF/UHF communication systems.
Abstract: In this paper we present a study of the ionospheric effects of a halo coronal mass ejection (CME) initiated on the Sun on September 20, 1999, and causing the largest magnetic storm during this month on September 22–23, 1999, with the hourly Dst index being −167 nT at ∼2400 UT on September 22. The recurrent CME on October 18 caused an even larger magnetic storm on October 22, 1999, with Dst of −231 nT at ∼0700 UT. The ionospheric effects of these two major magnetic storms are studied through their effects on a prototype of a Global Positioning System (GPS)-based navigation system called Wide Area Augmentation System (WAAS) being developed by the Federal Aviation Administration for use in the continental United States and their impact on global VHF/UHF communication systems. It is shown that the penetration of transient magnetospheric electric fields equatorward of the shielding region at midlatitudes, which have been well-correlated in the past with rapid changes in the well-known Dst index (or through its recently available high resolution 1-min counterpart the SYM-H index), can cause large increases of total electron content (TEC), TEC fluctuations, and saturated 250-MHz scintillation, and these, in turn, may have significant impacts on WAAS. The local time of Dst changes (and not just Dst magnitude) was found to be very important for WAAS, since the largest effects on TEC are seen near dusk. The prompt penetration of these magnetospheric electric fields all the way to the magnetic equator causes augmentation or inhibition of equatorial spread F. The global ionospheric response to these storms has been obtained from ground-based TEC observations with a GPS network and space-based in situ density and electric field measurements using the Republic of China Satellite-1 (ROCSAT-I) and several Defense Meteorological Satellite Program satellites. These prompt penetration electric fields cause VHF/UHF scintillations and GPS TEC variations at low latitudes in the specific longitude sector for which the early evening period corresponds to the time of rapid Dst variations and maximum Dst phase. The effects of the delayed ionospheric disturbance dynamo and those of decreased magnetospheric convection on postmidnight irregularity generation are shown to be confined to a part of the same longitude range that actively responded to the prompt penetration of electric fields in the early evening sector.

235 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used amplitude scintillation measurements of L1 (1.575MHz) signals from GPS satellites at Ascension Island (14.45° W, 7.95° S; magnetic latitude 16° S) during February-April, 1998, to compare amplitude scints with fluctuations of the total electron content (TEC).

228 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focused on the concentric wave propagation characteristics of the 2011 Tohoku earthquake and revealed the details of ionospheric disturbances by high-resolution GPS total electron content observation in Japan.
Abstract: All the details of ionospheric disturbances following the 2011 Tohoku Earthquake were first revealed by the high-resolution GPS total electron content observation in Japan. The initial ionospheric disturbance appeared as sudden depletions following small impulsive TEC enhancements ~7 minutes after the earthquake onset, near the epicenter. Then, concentric waves appeared to propagate in the radial direction with a velocity of 138–3,457 m/s. Zonally-extended enhancements of the TEC also appeared in the west of Japan. In the vicinity of the epicenter, short-period oscillations with a period of ~4 minutes were observed. This paper focuses on the concentric waves. The concentric pattern indicates that they had a point source. The center of these structures, termed the “ionospheric epicenter”, was located about 170 km from the epicenter in the southeast direction. According to the propagation characteristics, these concentric waves could be caused by atmospheric waves classified into three types: acoustic waves generated from a propagating Rayleigh wave, acoustic waves from the ionospheric epicenter, and atmospheric gravity waves from the ionospheric epicenter. The amplitude of the concentric waves was not uniform and was dependent on the azimuth of their propagation direction, which could not be explained by previously-proposed theory.

228 citations

Journal ArticleDOI
TL;DR: In this paper, the GPS satellite and receiver instrumental biases from 19 months of data and the study of their variation during that time are presented. But the main conclusion of this work is that due to the stability of the GPS instrumental biases, only an estimation or calibration of them from time to time is required.
Abstract: The main source of error in the estimation of TEC (total electron content) from dual Global Positioning System (GPS) data is the effect of the differential satellite and receiver instrumental delay biases. These biases are normally estimated simultaneously with the TEC. However, the additional estimation of the instrumental biases may constitute an insurmountable burden in some practical applications like real-time estimation of TEC, or the estimation may be difficult or correlated to the ionospheric parameters, particularly in situations where the TEC behavior may be harder to model (equatorial or auroral zone, ionospheric storms, etc.). A priori values of the instrumental biases, estimated under good conditions or with global networks, could solve those problems if we could determine how stable those instrumental biases are in time and how often we need to check or reestimate their values. In this paper we will present our estimation of the GPS satellite and receiver instrumental biases from 19 months of data and the study of their variation during that time. We will also show some situations of changes in the instrumental biases and the possible influence of antispoofmg (AS). The main conclusion of this work is that the variation of the estimated differential GPS satellite biases during the 19 months is smaller than 1 ns (1 ns = 2.86 × 1016 e/m2) in most of the cases, with a mean RMS of 0.15 ns. For the GPS receivers used, that variation is greater than for the satellites, with the larger variations corresponding to physical changes in the receivers. The difference of the estimated differential instrumental biases between two consecutive days is in practically all cases smaller than 0.5 ns for the GPS satellites and smaller than 1 ns for the GPS receivers. Regarding the influence of AS, we have detected some significant changes in the instrumental biases of some satellites and some stations whether AS is activated or not. Our main conclusion is that due to the stability of the GPS instrumental biases, only an estimation or calibration of them (under optimal conditions) from time to time is required.

224 citations

Journal ArticleDOI
TL;DR: In this article, large ionospheric variability is found at low to middle latitudes when a quasi-stationary planetary wave is specified in the winter stratosphere in the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere electrodynamics general circulation model for solar minimum conditions.
Abstract: [1] Large ionospheric variability is found at low to middle latitudes when a quasi-stationary planetary wave is specified in the winter stratosphere in the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere electrodynamics general circulation model for solar minimum conditions. The variability includes change of electric field/ion drift, F2 peak density and height, and the total electron content. The electric field/ion drift change is the largest near dawn in the numerical experiments. Analysis of model results suggests that, although the quasi-stationary planetary wave does not propagate deep into the ionosphere or to low latitudes due to the presence of critical layers and strong molecular dissipation, the planetary wave and tidal interaction leads to large changes in tides, which can strongly impact the ionosphere at low and middle latitudes through the E region wind dynamo. Large zonal gradients of zonal and meridional winds from the tidal components and the zonal gradient of electric conductivities at dawn can produce large convergence/divergence of Hall and Pedersen currents, which in turn produces a polarization electric field. The ionospheric changes are dependent on both the longitude and local time, and are determined by the amplitudes and phases of the superposing wave components. The model results are consistent with observed ionospheric changes at low and middle latitudes during stratospheric sudden warming events, when quasi-stationary planetary waves become large.

224 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023171
2022316
2021225
2020252
2019217
2018198