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Short term and real time prediction models


After strong geomagnetic storms, the ionosphere can be subject to significant alterations of the electronic density (ionospheric storm). The long term prediction models are not able to provide reliable predictions due to the large foF2 variations that can occur during ionospheric storms.
During these events, it is not easy to maintain HF radio communications because, for example, the large foF2 variations involve large MUF (maximum usable frequency in a radio link) variations that are very difficult to predict. For these reasons, it is necessary to develop short term prediction models (IFELMOR, ap(τ) model) to forecast foF2 a few hours in advance and to design models for the prediction of foF2 in real time (SIRMUP, ISWIRM, IMASHA) with the aim of providing HF operators with real-time or quasi-real-time assistance in choosing the optimal frequencies for radio links, even in the case of a highly disturbed ionosphere.
The development of models for predicting the ionospheric characteristics in real time, needs the continuous and automatic monitoring of the state of the ionosphere in real time at a useful number of stations.
The creation of a network of digisondes equipped with a specific software for the automatic scaling of ionograms (ARTIST, AUTOSCALA) has represented an essential step forward for the development of ionospheric models capable of supplying real time maps of the critical frequency of foF2 over the European region.
Even if real-time channel evaluation (RTCE) techniques are clearly more effective than any short term or nowcasting methods on a given radio link, nevertheless they cannot provide information over a large area, i.e., on all the potential radio links. For this reason, the two prediction models (SIRMUP&LKW e ISWIRM&LKW), developed to provide in real time both the MUF prediction for a given radio link (figure 1) and the prediction maps of the MUF over the European area (figure 2) have proved quite effective.

Figure 1 Comparisons between hourly measurements and predictions of the MUF obtained through real time models (SIRMUP&LKW, ISWIRM&LKW) for the radio link Inskip (U.K.)-Rome (Italy) on April 5, May 15, and November 4, 2005.

 

Figure 2 Real time prediction map of the MUF obtained through the SIRMUP&LKW model over the European region on September 27, 2008 at 14.00 UT.

 

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