Ljiljana R. Cander

Simplified ionospheric regional model for telecommunication applications

A simplified model of the key ionospheric characteristics of vertical incidence such as fo F2 M(3000)F2, h′F, foF1, and f0E that are used for prediction of operational parameters of HF telecommunication systems in a restricted area has been developed. The simplified ionospheric regional model (SIRM), is based upon the Fourier analysis of the monthly median values of these characteristics from seven ionospheric stations in Europe. It is shown that only 12 dominant Fourier coefficients, expressed as a function of local time (LT), solar activity and geographic latitude are sufficient to reproduce the main features of the diurnal, seasonal, and solar cycle behavior of the mid-latitude ionosphere under median conditions. The model is in a very suitable form for digital computer calculation of the characteristics for a given position, instant of time, and solar activity.

Ionospheric Prediction and Forecasting

Ionospheric Structure.- Ionospheric measurements for prediction and forecasting. Ionospheric prediction for radio propagation purposes.- Total electron content modelling and mapping.- Ionospheric forecasting.- Prediction and forecasting user manual.

Monitoring and Forecasting the Ionosphere Over Europe: The DIAS Project

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.

Twenty-four hour predictions of f0F2 using time delay neural networks

The use of time delay feed-forward neural networks to predict the hourly values of the ionospheric F2 layer critical frequency, f0F2, 24 hours ahead, have been examined. The 24 measurements of f0F2 per day are reduced to five coefficients with principal component analysis. A time delay line of these coefficients is then used as input to a feed-forward neural network. Also included in the input are the 10.7 cm solar flux and the geomagnetic index Ap. The network is trained to predict measured f0F2 data from 1965 to 1985 at Slough ionospheric station and validated on an independent validation set from the same station for the periods 1987–1990 and 1992–1994. The results are compared with two different autocorrelation methods for the years 1986 and 1991, which correspond to low and high solar activity, respectively.

On the potential applicability of the simplified ionospheric regional model to different midlatitude areas

The simplified ionospheric regional model (SIRM) was originally developed for modeling the most relevant ionospheric characteristics over Europe for radiocommunication purposes. The model, based mainly on the Fourier expansion of a reference past data set, is here adapted and applied to different sets of dishomogeneous periods of observed data coming from a sparse network of ionospheric stations in midlatitude areas, that is, northeastern North America, southeastern South America, northeast Asia, and southeast Australia. Notwithstanding the simple SIRM formulation and the reduced number of numerical coefficients involved, a good agreement has been found between modeled and observed monthly median values of ƒ0F2 and M(3000)F2 under different heliogeophysical conditions.

From COST 238 to COST 296: Four European COST Actions on Ionospheric Physics and Radio Propagation

COST (Co-operation in the field of Scientific and Technical Research) is an important instrument supporting co-operation among scientists and researchers across Europe now joining 35 member countries. Scientific projects in the COST framework are called COST Actions and have the objectives embodied in their respective Memorandum of Understanding (MoU). The main objectives of the COST Actions within the European ionospheric and radio propagation community have been: to study the influence of upper atmospheric conditions on terrestrial and Earth-space communications, to develop methods and techniques to improve existing and generate new ionospheric and propagation models over Europe for telecommunication and navigation applications and to transfer the results to the appropriate national and international organizations, institutions and industry dealing with the modern communication systems. This paper summarizes in brief the background and historical context of four ionospheric COST Actions and outlines the...

Ionospheric Space Weather Forecasting and Modelling

Ionospheric weather prediction, specification, forecasting and modelling techniques that enable the realization of effective space weather products are described. In the future these may eventually be adopted and implemented by decision-making authorities for space environment specifications, warnings, and forecasts, all of which need to be timely, accurate, and reliable.

Mid-Latitude Single Station F region Storm Morphology and Forecast

This paper describes certain aspects of the F region storm morphology based on vertical incidence measurements at single ionosonde station Chilton (51°.60′N, 358°.70′E). The topics discussed include requirements for better understanding of the ionospheric F region morphology and its forecasting under geomagnetically quiet and disturbed conditions. A few common storms during the years of low (1996 and 1997) and high (2000 and 2001) solar activity are considered as well as the Short-Term Ionospheric Forecasting (STIF) method by using two representative examples. The merits are stressed of near-real-time use of data to provide more accurate specification of the geomagnetically disturbed ionosphere and forecast its structure few hours in advance.

Ionospheric Measurements and Characteristics

The most important techniques systematically used for monitoring the ionized layers of the Earth’s upper atmosphere are based on propagation effects that influence radio waves travelling through the ionosphere.

The General Structure of the Ionosphere

The ionosphere of any planet is defined as that portion of the atmosphere where free electrons and ions of thermal energy exist under the control of the gravity and magnetic field of the planet.