A comparative study of GPS ionospheric scintillations and ionogram spread F over Sanya

Abstract. We analyze the data recorded during December 2011–November 2012 by a digital ionosonde and a GPS (Global Positioning System) scintillation and (total electron content) TEC receiver collocated at Sanya (109.6° E, 18.3° N; dip lat. 12.8° N), a low-latitude station in the Chinese longitude sector, to carry out a comparative study of ionospheric scintillations and spread F. A good consistency between the temporal variations of GPS scintillation (represented by the S4 index) and of ionogram spread F (represented by the QF index) is found in the pre-midnight period during equinox. However in the post-midnight period during equinox and in the period from post-sunset to pre-sunrise during June solstice, moderate spread F is seen without concurrent GPS scintillation. The possible cause responsible for the difference between post-midnight GPS scintillation and spread F during equinox could be due to the decaying of 400 m scale irregularities associated with equatorial spread F. Regarding the irregularities producing moderate QF and low S4 indices during June solstice, we suggest that the frequently observed sporadic E (Es) layer and the medium-scale traveling ionospheric disturbances (MSTIDs) over Sanya could play important roles in triggering the June solstitial spread-F events.

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Investigation of Low Latitude Spread-F Triggered by Nighttime Medium-Scale Traveling Ionospheric Disturbance

Remote Sensing ◽

10.3390/rs13050945 ◽

2021 ◽

Vol 13 (5) ◽

pp. 945

Author(s):

Zhongxin Deng ◽

Rui Wang ◽

Yi Liu ◽

Tong Xu ◽

Zhuangkai Wang ◽

...

Keyword(s):

Ionospheric Disturbance ◽

Phase Speed ◽

Morphological Processing ◽

Wave Number ◽

Occurrence Rate ◽

Electron Content ◽

Low Latitude ◽

Total Electron ◽

Medium Scale ◽

Spread F

In the current study, we investigated the mechanism of medium-scale traveling ionospheric disturbance (MSTID) triggering spread-F in the low latitude ionosphere using ionosonde observation and Global Navigation Satellite System-Total Electron Content (GNSS-TEC) measurement. We use a series of morphological processing techniques applied to ionograms to retrieve the O-wave traces automatically. The maximum entropy method (MEM) was also utilized to obtain the propagation parameters of MSTID. Although it is widely acknowledged that MSTID is normally accompanied by polarization electric fields which can trigger Rayleigh–Taylor (RT) instability and consequently excite spread-F, our statistical analysis of 13 months of MSTID and spread-F occurrence showed that there is an inverse seasonal occurrence rate between MSTID and spread-F. Thus, we assert that only MSTID with certain properties can trigger spread-F occurrence. We also note that the MSTID at night has a high possibility to trigger spread-F. We assume that this tendency is consistent with the fact that the polarization electric field caused by MSTID is generally the main source of post-midnight F-layer instability. Moreover, after thorough investigation over the azimuth, phase speed, main frequency, and wave number over the South America region, we found that the spread-F has a tendency to be triggered by nighttime MSTID, which is generally characterized by larger ΔTEC amplitudes.

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Functional model modification of precise point positioning considering the time-varying code biases of a receiver

Satellite Navigation ◽

10.1186/s43020-021-00040-4 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Baocheng Zhang ◽

Chuanbao Zhao ◽

Robert Odolinski ◽

Teng Liu

Keyword(s):

Precise Point Positioning ◽

Functional Model ◽

Geodetic Network ◽

Temporal Variations ◽

Gps Data ◽

Electron Content ◽

Time Varying ◽

Dual Frequency ◽

Total Electron ◽

Point Positioning

AbstractPrecise Point Positioning (PPP), initially developed for the analysis of the Global Positing System (GPS) data from a large geodetic network, gradually becomes an effective tool for positioning, timing, remote sensing of atmospheric water vapor, and monitoring of Earth’s ionospheric Total Electron Content (TEC). The previous studies implicitly assumed that the receiver code biases stay constant over time in formulating the functional model of PPP. In this contribution, it is shown this assumption is not always valid and can lead to the degradation of PPP performance, especially for Slant TEC (STEC) retrieval and timing. For this reason, the PPP functional model is modified by taking into account the time-varying receiver code biases of the two frequencies. It is different from the Modified Carrier-to-Code Leveling (MCCL) method which can only obtain the variations of Receiver Differential Code Biases (RDCBs), i.e., the difference between the two frequencies’ code biases. In the Modified PPP (MPPP) model, the temporal variations of the receiver code biases become estimable and their adverse impacts on PPP parameters, such as ambiguity parameters, receiver clock offsets, and ionospheric delays, are mitigated. This is confirmed by undertaking numerical tests based on the real dual-frequency GPS data from a set of global continuously operating reference stations. The results imply that the variations of receiver code biases exhibit a correlation with the ambient temperature. With the modified functional model, an improvement by 42% to 96% is achieved in the Differences of STEC (DSTEC) compared to the original PPP model with regard to the reference values of those derived from the Geometry-Free (GF) carrier phase observations. The medium and long term (1 × 104 to 1.5 × 104 s) frequency stability of receiver clocks are also significantly improved.

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Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

Annales Geophysicae ◽

10.5194/angeo-26-1751-2008 ◽

2008 ◽

Vol 26 (7) ◽

pp. 1751-1757 ◽

Cited By ~ 10

Author(s):

S. V. Thampi ◽

S. Ravindran ◽

T. K. Pant ◽

C. V. Devasia ◽

R. Sridharan

Keyword(s):

Seasonal Variability ◽

Seasonal Pattern ◽

Onset Time ◽

Critical Value ◽

Latitudinal Gradients ◽

Electron Content ◽

Total Electron ◽

Equatorial Spread F ◽

Spread F ◽

Definite Role

Abstract. In an earlier study, Thampi et al. (2006) have shown that the strength and asymmetry of Equatorial Ionization Anomaly (EIA), obtained well ahead of the onset time of Equatorial Spread F (ESF) have a definite role on the subsequent ESF activity, and a new "forecast parameter" has been identified for the prediction of ESF. This paper presents the observations of EIA strength and asymmetry from the Indian longitudes during the period from August 2005–March 2007. These observations are made using the line of sight Total Electron Content (TEC) measured by a ground-based beacon receiver located at Trivandrum (8.5° N, 77° E, 0.5° N dip lat) in India. It is seen that the seasonal variability of EIA strength and asymmetry are manifested in the latitudinal gradients obtained using the relative TEC measurements. As a consequence, the "forecast parameter" also displays a definite seasonal pattern. The seasonal variability of the EIA strength and asymmetry, and the "forecast parameter" are discussed in the present paper and a critical value for has been identified for each month/season. The likely "skill factor" of the new parameter is assessed using the data for a total of 122 days, and it is seen that when the estimated value of the "forecast parameter" exceeds the critical value, the ESF is seen to occur on more than 95% of cases.

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Reconstruction of Storm‐Time Total Electron Content Using Ionospheric Tomography and Artificial Neural Networks: A Comparative Study Over the African Region

Radio Science ◽

10.1029/2017rs006499 ◽

2018 ◽

Vol 53 (11) ◽

pp. 1328-1345 ◽

Cited By ~ 4

Author(s):

Jean Claude Uwamahoro ◽

Nigussie M. Giday ◽

John Bosco Habarulema ◽

Zama T. Katamzi‐Joseph ◽

Gopi Krishna Seemala

Keyword(s):

Neural Networks ◽

Artificial Neural Networks ◽

Comparative Study ◽

Total Electron Content ◽

Electron Content ◽

African Region ◽

Total Electron ◽

Ionospheric Tomography ◽

Artificial Neural

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Comparison of GPS TEC with IRI models of 2007, 2012, AND 1 2016 over Sukkur, Pakistan

Natural and Applied Sciences International Journal (NASIJ) ◽

10.47264/idea.nasij/1.1.1 ◽

2020 ◽

Vol 1 (1) ◽

pp. 1-10

Author(s):

Adil Hussain ◽

Munawar Shah

Keyword(s):

Global Positioning System ◽

Electron Content ◽

Iri Model ◽

Low Latitude ◽

Total Electron ◽

Gps Tec ◽

Global Positioning ◽

Radio Signals ◽

Ionospheric Scintillations ◽

Latitude Region

The international reference ionosphere (IRI) models have been widely used for correcting the ionospheric scintillations at different altitude levels. An evaluation on the performance of VTEC correction from IRI models (version 2007, 2012 and 2016) over Sukkur, Pakistan (27.71º N, 68.85º E) is presented in this work. Total Electron Content (TEC) from IRI models and GPS in 2019 over Sukkur region are compared. The main aim of this comparative analysis is to improve the VTEC in low latitude Sukkur, Pakistan. Moreover, this study will also help us to identify the credible IRI model for the correction of Global Positioning System (GPS) signal in low latitude region in future. The development of more accurate TEC finds useful applications in enhancing the extent to which ionospheric influences on radio signals are corrected. VTEC from GPS and IRI models are collected between May 1, 2019 and May 3, 2019. Additionally, Dst and Kp data are also compared in this work to estimate the geomagnetic storm variations. This study shows a good correlation of 0.83 between VTEC of GPS and IRI 2016. Furthermore, a correlation of 0.82 and 0.78 is also recorded for IRI 2012 and IRI 2007 respectively, with VTEC of GPS. The IRI TEC predictions and GPS-TEC measurements for the studied days reveal the potential of IRI model as a good candidate over Pakistan.

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Adaptive Modeling of the Global Ionosphere Vertical Total Electron Content

Remote Sensing ◽

10.3390/rs12111822 ◽

2020 ◽

Vol 12 (11) ◽

pp. 1822

Author(s):

Eren Erdogan ◽

Michael Schmidt ◽

Andreas Goss ◽

Barbara Görres ◽

Florian Seitz

Keyword(s):

Total Electron Content ◽

Temporal Variations ◽

Model Parameters ◽

Electron Content ◽

Vertical Total Electron Content ◽

Model Uncertainties ◽

Data Set ◽

Total Electron ◽

B Spline ◽

Run Time

The Kalman filter (KF) is widely applied in (ultra) rapid and (near) real-time ionosphere modeling to meet the demand on ionosphere products required in many applications extending from navigation and positioning to monitoring space weather events and naturals disasters. The requirement of a prior definition of the stochastic models attached to the measurements and the dynamic models of the KF is a drawback associated with its standard implementation since model uncertainties can exhibit temporal variations or the time span of a given test data set would not be large enough. Adaptive methods can mitigate these problems by tuning the stochastic model parameters during the filter run-time. Accordingly, one of the primary objectives of our study is to apply an adaptive KF based on variance component estimation to compute the global Vertical Total Electron Content (VTEC) of the ionosphere by assimilating different ionospheric GNSS measurements. Secondly, the derived VTEC representation is based on a series expansion in terms of compactly supported B-spline functions. We highlight the morphological similarity of the spatial distributions and the magnitudes between VTEC values and the corresponding estimated B-spline coefficients. This similarity allows for deducing physical interpretations from the coefficients. In this context, an empirical adaptive model to account for the dynamic model uncertainties, representing the temporal variations of VTEC errors, is developed in this work according to the structure of B-spline coefficients. For the validation, the differential slant total electron content (dSTEC) analysis and a comparison with Jason-2/3 altimetry data are performed. Assessments show that the quality of the VTEC products derived by the presented algorithm is in good agreement, or even more accurate, with the products provided by IGS ionosphere analysis centers within the selected periods in 2015 and 2017. Furthermore, we show that the presented approach can be applied to different ionosphere conditions ranging from very high to low solar activity without concerning time-variable model uncertainties, including measurement error and process noise of the KF because the associated covariance matrices are computed in a self-adaptive manner during run-time.

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Comparison of simultaneous variations of the ionospheric total electron content and geomagnetic field associated with strong earthquakes

Natural Hazards and Earth System Science ◽

10.5194/nhess-1-53-2001 ◽

2001 ◽

Vol 1 (1/2) ◽

pp. 53-59 ◽

Cited By ~ 7

Author(s):

Sh. Naaman ◽

L. S. Alperovich ◽

Sh. Wdowinski ◽

M. Hayakawa ◽

E. Calais

Keyword(s):

Total Electron Content ◽

Vertical Displacement ◽

Temporal Variations ◽

Electron Content ◽

Geomagnetic Disturbances ◽

Total Electron ◽

Strong Earthquakes ◽

Ionospheric Total Electron Content ◽

Geomagnetic Observations ◽

Gps Observations

Abstract. In this paper, perturbations of the ionospheric Total Electron Content (TEC) are compared with geomagnetic oscillations. Comparison is made for a few selected periods, some during earthquakes in California and Japan and others at quiet periods in Israel and California. Anomalies in TEC were extracted using Global Positioning System (GPS) observations collected by GIL (GPS in Israel) and the California permanent GPS networks. Geomagnetic data were collected in some regions where geomagnetic observatories and the GPS network overlaps. Sensitivity of the GPS method and basic wave characteristics of the ionospheric TEC perturbations are discussed. We study temporal variations of ionospheric TEC structures with highest reasonable spatial resolution around 50 km. Our results show no detectable TEC disturbances caused by right-lateral strike-slip earthquakes with minor vertical displacement. However, geomagnetic observations obtained at two observatories located in the epicenter zone of a strong dip-slip earthquake (Kyuchu, M = 6.2, 26 March 1997) revealed geomagnetic disturbances occurred 6–7 h before the earthquake.

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Tropospheric dispersive phase anomalies during heavy rain detected by L-band InSAR and their interpretation

Earth Planets and Space ◽

10.1186/s40623-021-01470-9 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Naufal Setiawan ◽

Masato Furuya

Keyword(s):

Total Electron Content ◽

Heavy Rain ◽

Electron Content ◽

Dispersive Component ◽

Total Electron ◽

First Order ◽

Dispersive Effect ◽

L Band ◽

Sporadic E ◽

Dispersive Phase

AbstractThe split-spectrum method (SSM) can largely isolate and correct for the ionospheric contribution in the L-band interferometric synthetic aperture radar (InSAR). The standard SSM is performed on the assumption of only the first-order ionospheric dispersive effect, which is proportional to the total electron content (TEC). It is also known that during extreme atmospheric events, either originated from the ionosphere or in the troposphere, other dispersive effects do exist and potentially provide new insights into the dynamics of the atmosphere, but there have been few detection reports of such signals by InSAR. We apply L-band InSAR into heavy rain cases and examine the applicability and limitation of the standard SSM. Since no events such as earthquakes to cause surface deformation took place, the non-dispersive component is apparently attributable to the large amount of water vapor associated with heavy rain, whereas there are spotty anomalies in the dispersive component that are closely correlated with the heavy rain area. The ionosonde and Global Navigation Satellite System (GNSS) rate of total electron content index (ROTI) map both show little anomalies during the heavy rain, which suggests few ionospheric disturbances. Therefore, we interpret that the spotty anomalies in the dispersive component of the standard SSM during heavy rain are originated in the troposphere. While we can consider two physical mechanisms, one is runaway electron avalanche and the other is the dispersive effect due to rain, comparison with the observations from the ground-based lightning detection network and rain gauge data, we conclude that the rain dispersive effect is spatiotemporally favorable. We further propose a formulation to examine if another dispersive phase than the first-order TEC effect is present and apply it to the heavy rain cases as well as two extreme ionospheric sporadic-E events. Our formulation successfully isolates the presence of another dispersive phase during heavy rain that is in positive correlation with the local rain rate. In comparison with other dispersive phases during Sporadic-E episodes, the dispersive heavy rain phases seem to have the same order of magnitude with the ionospheric higher order effects.

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Hemispheric asymmetry of the ionospheric variation during major sudden stratospheric warming events

10.5194/egusphere-egu2020-20247 ◽

2020 ◽

Author(s):

Donghe Zhang ◽

Jing Liu

Keyword(s):

Hemispheric Asymmetry ◽

Relative Strength ◽

Magnetic Equator ◽

Electron Content ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Total Electron ◽

The North ◽

Latitudinal Variations ◽

The Difference

The hemispheric asymmetry of the ionospheric variation in the American sector (45&#176;N~45&#176;S, MLAT; 80&#176;~60&#176;W) is studied with total electron content (TEC) data during major sudden stratospheric warming events. The amplitude (AM2) and relative strength (RSM2) of the semi-diurnal lunar tidal component (M2) of TEC are analyzed. RSM2 is the ratio between the energy of M2 and the energy of all the studied tidal components. The magnitudes of AM2 and RSM2 exhibit clear hemispheric and latitudinal variations. The AM2 in the north of the magnetic equator tends to occur at lower magnetic latitudes than the AM2 in the south of the magnetic equator. The RSM2 exhibits similar features as the AM2 but the difference is more distinct. We suggest that such hemispheric asymmetry of M2 parameters is related to the hemispheric asymmetry of the EIA and the latitudinal variation of the amplitude of the solar tidal components in winter.

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Correlation between wave activities in different layers of the atmosphere

10.5194/egusphere-egu2020-6863 ◽

2020 ◽

Author(s):

Konstantin Ratovsky ◽

Irina Medvedeva ◽

Anna Yasyukevich ◽

Boris Shpynev ◽

Denis Khabituev

Keyword(s):

Correlation Coefficients ◽

Internal Gravity Wave ◽

Basic Research ◽

Temporal Variations ◽

Wave Activity ◽

Electron Content ◽

Russian Science ◽

Period Range ◽

Total Electron ◽

Mesopause Temperature

We study the correlation between wave activities in different layers of the atmosphere. The variability of the measured characteristic in the range of internal gravity wave periods is used as a proxy of wave activity. In the case of ground-based measurements, we consider temporal variations with periods less than ~ 6 hours; while in the case of satellite measurements we take into account spatial variations with periods less than ~ 1000 km. The wave activity is calculated as the standard deviation of variations in the indicated period range with averaging over one day. The aim of the study is to detect a correlation between day-to-day variations of wave activity in different layers of the atmosphere. Correlation coefficients are calculated for various intervals from one month to one year. Correlation analysis reveals the potential relationship between wave phenomena in the stratosphere, mesosphere and ionosphere. The study uses the following characteristics. The ionospheric characteristics are the peak electron density from the Irkutsk ionosonde (52.3 N, 104.3 E) and the total electron content from the Irkutsk GPS receiver. The characteristic of the mesosphere is the mesopause temperature from spectrometric measurements of the OH emission (834.0 nm, band (6-2)) near Irkutsk (51.8 N, 103.1 E, Tory). The stratospheric characteristic is the vertical gas velocity at 1 hPa from the ERA-Interim reanalysis (apps.ecmwf.int/datasets/data/).This study was supported by the Grant of the Russian Science Foundation (Project N 18-17-00042).&#160;The observational results were obtained using the equipment of Center for Common Use &#171;Angara&#187; http: //ckp-rf.ru/ckp/3056/ within budgetary funding of Basic Research program II.12.

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