The Experts below are selected from a list of 165420 Experts worldwide ranked by ideXlab platform
Jens Berdermann - One of the best experts on this subject based on the ideXlab platform.
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An ionospheric index suitable for estimating the degree of ionospheric perturbations
Journal of Space Weather and Space Climate, 2018Co-Authors: Volker Wilken, Martin Kriegel, Norbert Jakowski, Jens BerdermannAbstract:Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet (AE), Kp , Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC (ROTI), the scintillation indices S4 and the Along-Arc TEC Rate index (AATR) index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.
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An ionospheric index suitable for estimating the degree of ionospheric perturbations
Journal of Space Weather and Space Climate, 2018Co-Authors: Volker Wilken, Martin Kriegel, Norbert Jakowski, Jens BerdermannAbstract:Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ (ϕ ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.
Yunbin Yuan - One of the best experts on this subject based on the ideXlab platform.
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real time precise point positioning rtppp with raw observations and its application in real time regional ionospheric vtec modeling
Journal of Geodesy, 2018Co-Authors: Baocheng Zhang, Yunbin Yuan, Min LiAbstract:Precise Point Positioning (PPP) is an absolute positioning technology mainly used in post data processing. With the continuously increasing demand for real-time high-precision applications in positioning, timing, retrieval of atmospheric parameters, etc., Real-Time PPP (RTPPP) and its applications have drawn more and more research attention in recent years. This study focuses on the models, algorithms and ionospheric applications of RTPPP on the basis of raw observations, in which high-precision slant ionospheric delays are estimated among others in real time. For this purpose, a robust processing strategy for multi-station RTPPP with raw observations has been proposed and realized, in which real-time data streams and State-Space-Representative (SSR) satellite orbit and clock corrections are used. With the RTPPP-derived slant ionospheric delays from a regional network, a real-time regional ionospheric Vertical Total Electron Content (VTEC) modeling method is proposed based on Adjusted Spherical Harmonic Functions and a Moving-Window Filter. SSR satellite orbit and clock corrections from different IGS analysis centers are evaluated. Ten globally distributed real-time stations are used to evaluate the positioning performances of the proposed RTPPP algorithms in both static and kinematic modes. RMS values of positioning errors in static/kinematic mode are 5.2/15.5, 4.7/17.4 and 12.8/46.6 mm, for north, east and up components, respectively. Real-time slant ionospheric delays from RTPPP are compared with those from the traditional Carrier-to-Code Leveling (CCL) method, in terms of function model, formal precision and between-receiver differences of short baseline. Results show that slant ionospheric delays from RTPPP are more precise and have a much better convergence performance than those from the CCL method in real-time processing. 30 real-time stations from the Asia-Pacific Reference Frame network are used to model the ionospheric VTECs over Australia in real time, with slant ionospheric delays from both RTPPP and CCL methods for comparison. RMS of the VTEC differences between RTPPP/CCL method and CODE final products is 0.91/1.09 TECU, and RMS of the VTEC differences between RTPPP and CCL methods is 0.67 TECU. Slant Total Electron Contents retrieved from different VTEC models are also validated with epoch-differenced Geometry-Free combinations of dual-frequency phase observations, and mean RMS values are 2.14, 2.33 and 2.07 TECU for RTPPP method, CCL method and CODE final products, respectively. This shows the superiority of RTPPP-derived slant ionospheric delays in real-time ionospheric VTEC modeling.
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Multi-dimensional distribution of near-field ionospheric disturbances produced by the 2015 Mw7.8 Nepal earthquake
Journal of Asian Earth Sciences, 2017Co-Authors: Jun Tang, Yunbin YuanAbstract:Abstract Ionospheric anomalies possibly associated with large earthquakes, particularly coseismic ionospheric disturbances, have been detected by global positioning system (GPS). A large Nepal earthquake with magnitude Mw7.8 occurred on April 25, 2015. In this paper, we investigate the multi-dimensional distribution of near-field coseismic ionospheric disturbances (CIDs) using total electron content (TEC) and computerized ionospheric tomography (CIT) from regional GPS observational data. The results show significant ionospheric TEC disturbances and interesting multi-dimensional structures around the main shock. Regarding the TEC changes, coseismic ionospheric disturbances occur approximately 10–20 min after the earthquake northeast and northwest of epicentre. The maximum ridge-to-trough amplitude of CIDs is up to approximately 0.90 TECU/min. Propagation velocities of the TEC disturbances are 1.27 ± 0.06 km/s and 1.91 ± 0.38 km/s. It is believed that the ionospheric disturbances are triggered by acoustic and Rayleigh waves. Tomographic results show that the three-dimensional distribution of ionospheric disturbances obviously increases at an altitude of 300 km above the surrounding epicentre, predominantly in the entire region between 200 km and 400 km. Significant ionospheric disturbances appear at 06:30 UT from tomographic images. This study reveals characteristics of an ionospheric anomaly caused by the Nepal earthquake.
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Ionospheric eclipse factor method (IEFM) for determining the ionospheric delay using GPS data
Progress in Natural Science, 2004Co-Authors: Yunbin YuanAbstract:Abstract By establishing the ionospheric eclipse factor (IEF) λ of the ionospheric pierce point (IPP) and its ionospheric influence factor (IFF) λ, and combining λ, λ with t of IPP, a new method of modeling high-precision ionospheric delay using GPS data—ionospheric eclipse factor method (IEFM)—is presented in this paper. The IEFM can effectively select the proper ionospheric models to model the total electron content (TEC) with different changes corresponding to annual, seasonal and diurnal variations. Initial experimental results show that the correction precision of ionospheric delay modeled by the IEFM seems to be close to that of using L3 GPS observations to directly correct the corresponding ionospheric delay.
Shuanggen Jin - One of the best experts on this subject based on the ideXlab platform.
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GNSS ionospheric seismology: Recent observation evidences and characteristics
Earth-Science Reviews, 2015Co-Authors: Shuanggen Jin, Giovanni Occhipinti, Rui JinAbstract:The detail and nature of earthquakes are still challenging from traditional technique observations, e.g., seismometers and strong motion accelerographs. Nowadays, the ionospheric total electron content (TEC) can be obtained from ground-based global navigation satellite systems (GNSS) and space-borne GNSS Radio Occultation, which can be used to investigate the seismo-ionospheric disturbances and may provide insights on the earthquake. In this paper, GNSS ionospheric seismology is presented and reviewed, including methods, observation results and characteristics. Case studies of the 2008 Wenchuan earthquake and 2011 Japan earthquake are presented using ground-based GNSS observations. Significant co-/post-seismic ionospheric anomalies are found from continuous GNSS observations near the epicenters, showing that the seismic ionospheric total electron content (TEC) disturbances were derived mainly from the main shock. The detailed pattern and evolution of the ionospheric disturbance are revealed by denser GNSS observations. Some simulations explore the nature of the ionospheric perturbation, highlighting that acoustic-gravity waves are generated close to the epicenter, and that surface Rayleigh waves and tsunamis generate in the atmosphere/ionosphere acoustic and gravity waves respectively. These waves are induced by solid-Earth/ocean and atmosphere coupling at the ground or ocean interface with the atmosphere propagating upward until the ionosphere create strong perturbation in plasma density and plasma velocity.
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Ionospheric Sounding Using GNSS-RO
GNSS Remote Sensing, 2013Co-Authors: Shuanggen Jin, Estel Cardellach, Feiqin XieAbstract:The GNSS signal will be bent from GNSS transmitters and LEO satellites when the signal goes through Earth’s ionosphere. With the improvement of GNSS-RO technique and more GNSS-RO missions, ionospheric parameters can be retrieved, including TEC and ionospheric electron density. In this chapter, the theory and methods of ionospheric inversion from GNSS RO are introduced as well as their applications in the ionosphere, such as establishing ionospheric models, monitoring ionospheric anomalies and Ionospheric scintillation.
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Ground GNSS Ionosphere Sounding
GNSS Remote Sensing, 2013Co-Authors: Shuanggen Jin, Estel Cardellach, Feiqin XieAbstract:Ionospheric delay will bring errors for GNSS navigation and positioning when the electromagnetic wave signal goes through the earth’s ionosphere from satellites to receivers. The amount of ionospheric delay of GNSS varies from a few meters to decades of meters, but could reach more than decades of meters during severe ionosphere storms. In contrast, the GNSS ionospheric delay may provide some useful information on the ionosphere, e.g. the total electron content (TEC). In this chapter, the theory and methods of ground-based GNSS ionospheric sounding are introduced, including vertical TEC, differential code biases, 2-D and 3-D ionospheric mapping. In addition, some applications are presented and discussed, e.g., GNSS TEC climatology, solar flare and storms response and co-seismic ionospheric behaviors.
Volker Wilken - One of the best experts on this subject based on the ideXlab platform.
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An ionospheric index suitable for estimating the degree of ionospheric perturbations
Journal of Space Weather and Space Climate, 2018Co-Authors: Volker Wilken, Martin Kriegel, Norbert Jakowski, Jens BerdermannAbstract:Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet (AE), Kp , Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC (ROTI), the scintillation indices S4 and the Along-Arc TEC Rate index (AATR) index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.
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An ionospheric index suitable for estimating the degree of ionospheric perturbations
Journal of Space Weather and Space Climate, 2018Co-Authors: Volker Wilken, Martin Kriegel, Norbert Jakowski, Jens BerdermannAbstract:Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ (ϕ ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.
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NEW IONOSPHERIC MODELS FOR MONITORING AND FORECASTING IONOSPHERIC WEATHER
2011Co-Authors: Norbert Jakowski, Volker Wilken, Mohammed Mainul Hoque, Tatjana Gerzen, Claudia Borries, Klaus-dieter Missling, Henrike Barkmann, Mirco TeglerAbstract:The ionospheric plasma may cause range errors of up to 100m at L-band signals used in Global Navigation Satellite Systems (GNSS). Hence, correction of ionospheric propagation errors is an important task for single frequency users and related augmentation systems such as WAAS in US and EGNOS in Europe. In a first order approximation the range error is proportional to the integral of the electron density along the ray path (Total Electron Content - TEC). Therefore, knowledge of the ionospheric TEC can effectively be used to correct ionospheric errors. In this talk we review new ionospheric models we have recently developed for imaging the ionospheric behaviour. The modelled parameters such as TEC and electron density are functions of geographic/geomagnetic location, local time and solar flux as a measure of solar activity. The model coefficients are deduced from input data by least squares methods. The models are used in the operational space weather and ionosphere data service SWACI (http://swaciweb.dlr.de ) at DLR Neustrelitz for calibrating, mapping and forecasting TEC and for starting 3D reconstructions of the ionospheric plasma density. Furthermore, basic features of the models for TEC and F2 layer peak density NmF2 including preliminary validation results are reported. The multifunctional use of the models in the SWACI service is described.
Feiqin Xie - One of the best experts on this subject based on the ideXlab platform.
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Ionospheric Sounding Using GNSS-RO
GNSS Remote Sensing, 2013Co-Authors: Shuanggen Jin, Estel Cardellach, Feiqin XieAbstract:The GNSS signal will be bent from GNSS transmitters and LEO satellites when the signal goes through Earth’s ionosphere. With the improvement of GNSS-RO technique and more GNSS-RO missions, ionospheric parameters can be retrieved, including TEC and ionospheric electron density. In this chapter, the theory and methods of ionospheric inversion from GNSS RO are introduced as well as their applications in the ionosphere, such as establishing ionospheric models, monitoring ionospheric anomalies and Ionospheric scintillation.
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Ground GNSS Ionosphere Sounding
GNSS Remote Sensing, 2013Co-Authors: Shuanggen Jin, Estel Cardellach, Feiqin XieAbstract:Ionospheric delay will bring errors for GNSS navigation and positioning when the electromagnetic wave signal goes through the earth’s ionosphere from satellites to receivers. The amount of ionospheric delay of GNSS varies from a few meters to decades of meters, but could reach more than decades of meters during severe ionosphere storms. In contrast, the GNSS ionospheric delay may provide some useful information on the ionosphere, e.g. the total electron content (TEC). In this chapter, the theory and methods of ground-based GNSS ionospheric sounding are introduced, including vertical TEC, differential code biases, 2-D and 3-D ionospheric mapping. In addition, some applications are presented and discussed, e.g., GNSS TEC climatology, solar flare and storms response and co-seismic ionospheric behaviors.