This paper demonstrates the concept and practical examples of instantaneous mapping of regional ionosphere, based on GPS observations from the State of Ohio continuously operating reference stations (CORS) network. Interpolation/prediction techniques, such as kriging (KR) and the Multiquadric Model (MQ), which are suitable for handling multi-scale phenomena and unevenly distributed data, were used to create total electron content (TEC) maps. Their computational efficiency (especially the MQ technique) and the ability to handle undersampled data (especially kriging) are particularly attractive. Presented here are the preliminary results based on GPS observations collected at five Ohio CORS stations (~100 km sta-tion separation and 1-second sampling rate). Dual frequency carrier phase and code GPS observations were used. A zero-difference approach was used for absolute TEC recovery. The quality of the ionosphere rep-resentation was tested by comparison to the International GPS Service (IGS) Global Ionosphere Maps (GIMs), which were used as a reference.

/pdf/regional-ionosphere-mapping-with-kriging-and-multiquadric-l8ubpph4nx.pdf

Regional Ionosphere Mapping with Kriging and Multiquadric Methods

[1] In this paper a climatology model of total electron content (TEC) over China has been developed on the basis of the empirical orthogonal function (EOF) analysis using Global Positioning System (GPS) data from the International Global Navigation Satellite System Service (IGS) and Crust Movement Observation Network of China (CMONOC) covering almost the whole Chinese sector during 1996–2004. The model well represents observational data with mean bias of −0.00994 TECU (1 TECU = 1.0 × 1016 el· m−2) and standard deviation of 5.42 TECU. Then the EOF model and IRI have been used in three-dimensional variational (3DVAR) data assimilation experiments separately, and results reveal that the ability of assimilation nowcasting for the EOF model is better as it provides a more authentic background.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2007RS003629

An empirical orthogonal function model of total electron content over China

Knowledge of the state of the upper atmosphere, and in particular its ionospheric part, is very important in several applications affected by space weather, especially the communications and navigation systems that rely on radio transmission. To better classify the ionosphere and forecast its disturbances over Europe, a data collection endeavour called the European Digital Upper Atmosphere Server (DIAS) was initiated in 2004 by a consortium formed around several European ionospheric stations that transmit in real-time ionospheric parameters automatically scaled. The DIAS project is a collaborative venture of eight institutions funded by the European Commission eContent Programme. The project seeks to improve access to digital information collected by public European institutes and to expand its use. The main objective of the DIAS project is to develop a pan-European digital data collection describing the state of the upper atmosphere, based on real-time information and historical data collections provided by most of the operating ionospheric stations in Europe. Various groups of users require data specifying upper atmospheric conditions over Europe for nowcasting and forecasting purposes. The DIAS system is designed to distribute such information. The successful operation of DIAS is based on the effective use of observational data in operational applications through the development of new added-value ionospheric products and services that best fit the needs of the market. DIAS is a unique European system, and its continuous operation will efficiently support radio propagation services with the most reliable information. DIAS began providing services to users in August 2006. The Need for Accurate Ionospheric Products Radio frequency communications and satellite positioning and navigation systems are applications most affected by ionospheric disturbances. Such disturbances can cause drastic and large-scale changes in the usable ranges of high frequency (HF) or below HF bands affecting standard ground-to-ground and submarine communication systems. The characteristics of an ionospheric propagation channel, whether it is HF or transionospheric frequencies, are highly variable on timescales ranging from a few seconds to the 11-year solar cycle. Even during its quietest periods, the Sun produces electromagnetic radiation and solar wind, both of which can affect a variety of geomagnetic and ionospheric phenomena, which in turn affect radio waves propagating through the ionosphere. Hence day-to-day and hour-to-hour changes in propagation channel characteristics can occur.

/pdf/monitoring-and-forecasting-the-ionosphere-over-europe-the-3z5pc17aew.pdf

Monitoring and Forecasting the Ionosphere Over Europe: The DIAS Project

The present study examines the ionospheric Total Electron Content (TEC) variations in the lower mid-latitude Turkish region from the Turkish permanent GNSS network (TPGN) and International GNSS Services (IGS) observations during the years 2009 to 2017. The corresponding vertical TEC (VTEC) predicted by Kriging and NeQuick-2 models are evaluated to realize their efficacy over the country. We studied the diurnal, seasonal and spatial pattern of VTEC variation and tried to estimate by a new mathematical model using the long term of 9 years VTEC data. The diurnal variation of VTEC demonstrates a normal trend with its gradual enhancement from dawn to attain a peak around 09:00–14.00 UT and reaching the minimum level after 22.00 UT. The seasonal behavior of VTEC indicates a strong semi-annual variation of VTEC with maxima in September equinox followed by March equinox and minima in June solstice followed by December solstice. Also, the spatial variation in VTEC depicts a meaningful longitudinal/latitudinal pattern altering with seasons. It decreases longitudinally from the west to the east during March equinox and June solstice increases with latitude. The comparative analysis among the GNSS-VTEC, Kriging, NeQuick and the proposed mathematical model are evaluated with the help one way ANOVA test. The analysis shows that the null hypothesis of the models during storm and quiet days are accepted and suggesting that all models are statistically significantly equivalent from each other. We believe the outcomes from this study would complement towards a relatively better understanding of the lower mid-latitude VTEC variation over the Turkish region and analogous latitudes over the globe.

Mathematical modelling of ionospheric TEC from Turkish permanent GNSS Network (TPGN) observables during 2009–2017 and predictability of NeQuick and Kriging models

[1] The solar eclipse of 11 August 1999 was total along a belt crossing Central Europe, where there is a high density of magnetic observatories. We studied the transient geomagnetic effects produced by the temporary cutoff of the ionizing solar radiations during the eclipse. It is the first case in which the phenomenon has been analysed in a multisite context. For observatories along the umbra path, a model based on the equivalent electric current schema is proposed.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005JA011499

Modeling the geomagnetic effects caused by the solar eclipse of 11 August 1999

Monthly median maps of ionospheric foF2 parameter show considerable discrepancies between the actual measurements and the values detected from the maps. Different instantaneous mapping techniques applied to randomly sparsed measurements give better agreement than monthly median maps. The objective of this paper is to present the PLES instantaneous mapping model for foF2 and M(3000)F2 that has been recommended as the best achievement of the COST 251 European Action. The method combines monthly median maps of ionospheric characteristic and a set of screen points consisting of measurements for a single moment of time as well as single station long-term models.

COST 251 recommended instantaneous mapping model of ionospheric characteristics — PLES

Instantaneous mapping methods for hourly observations were developed within the COST 251 European Action. The hourly maps of foF2 for eclipse day are available on the web page http://www.cbk.waw.pl/rwc/idce.html of the Ionospheric Despatch Centre in Europe. However, the eclipse effect on the ionosphere requires more frequent time scale for the observations than 1 hour. This paper presents the results of maps of foF2, foF1, foE with the use of 5-minute measurements during the eclipse of 11 August 1999. The instantaneous maps are shown be a useful tool to study the effect of the solar eclipse upon the ionosphere.

Instantaneous mapping of ionospheric characteristics using 5-minute measurements for the day of the total solar eclipse of 11 August 1999

Single-station models of ionospheric foF2 parameter usable for prediction and instantaneous mapping

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COST 251 recommended instantaneous mapping model of ionospheric characteristics — PLES

Instantaneous mapping of ionospheric characteristics using 5-minute measurements for the day of the total solar eclipse of 11 August 1999

Single-station models of ionospheric foF2 parameter usable for prediction and instantaneous mapping