doi:10.1016/j.asr.2006.08.008
Copyright © 2006 COSPAR Published by Elsevier Ltd.
A prediction model of foF2 over periods of severe geomagnetic activity
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L. Perrone
, a,
, M. Pietrellaa and B. Zolesia
aIstituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome 00143, Italy
Received 22 December 2005;
revised 12 July 2006;
accepted 15 August 2006.
Available online 5 December 2006.
Abstract
A prediction procedure of the hourly values of the critical frequency of the F2 ionospheric layer, foF2, based on the geomagnetic index, is presented. The geomagnetic index used in this study is the time-weighted accumulation magnetic index ap(τ) based on the recent past history of the planetary index ap.
The procedure is based on an empirical relationship between the ratio log(NmF2(t)/NmF2M(t)) and ap(τ), where NmF2(t) is the hourly maximum electron density at the F2 peak layer and NmF2M(t) is its ‘quiet’ value. The prediction of foF2 has been calculated during periods of severe magnetic activity in the current solar cycle 23 using data processed at the Rome ionospheric observatory. The performance of the model, during negative ionospheric storms, can be considered satisfactory, given that the root mean square (r.m.s.), calculated between measured and forecasted foF2, ranged between 0.74–2.0 MHz.
Keywords: Ionosphere; Ionospheric storms; F2 layer; Prediction model; Geomagnetic index
Fig. 1. The occurrence of negative ionospheric storms at different ap(τ) levels.
Fig. 2. Number of negative ionospheric storms divided for seasons and for different ap(τ) levels.
Fig. 3. (A) Negative ionospheric storms onset occurrence at different hour intervals. (B) Geomagnetic storms occurrence with ap(τ)
32 at different hours intervals.
Fig. 4. The time behaviour of foF2 observed, forecasted and of the ‘daily’ mean for 30 March–2 April 2001.
Fig. 5. The time behaviour of foF2 observed, forecasted and of the ‘daily’ mean for 10–14 April 2001.
Fig. 6. The time behaviour of foF2 observed, forecasted and of the ‘daily’ mean for 4–8 November 2001.
Fig. 7. The time behaviour of foF2 forecasted with the IRI Storm Model, ap(τ) model and observed values for four storm days.
Table 1.
ap(τ) levels

Table 2.
Hours (LT) intervals

Table 3.
r.m.s. values calculated for the storm days


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