An upgrade of the solar-wind-driven empirical model for the middle latitude ionospheric storm-time response

Abstract

Based on recent advances in ionospheric storm dynamics that correlate the ionospheric storm effects with space weather parameters such as the magnitude of the interplanetary magnetic field (IMF), its rate of change and the IMF's orientation in the north–south direction and on the availability of these parameters in real time by NASA ACE spacecraft from the vantage L1 point, an empirical storm-time ionospheric model for the middle latitude ionosphere, namely STIM, was recently envisaged. STIM is significantly upgraded and validated here. The model introduces a correction factor to the quiet daily ionospheric variation to anticipate storm conditions. It is triggered by an alert signal for upcoming ionospheric disturbances obtained from the analysis of the IMF measurements provided by ACE spacecraft. In its final version, STIM method includes quantitative criteria for the online analysis of the ACE's observations. The determination of the ionospheric storm onset and the empirical formulation of the ionospheric storm-time response, both in terms of the local time and the latitude of the observation point are also specified here. STIM's forecasts are provided from 13 to 45 h ahead for any middle latitude ionospheric location. Validation tests carried out for 27 storm-time intervals and for four European locations show that the model captures successfully the onset and the recovery of the ionospheric disturbance and follows sufficiently the disturbance pattern, providing also significant improvement over climatology during storm days. STIM was also compared with two well-known prediction models, the IRI2001 and the GCAM, and the findings demonstrate improved performance in favour of STIM, in both quantitative and qualitative aspect. In general, the results presented here support the efficiency of the proposed methodology in providing reliable ionospheric forecasts at middle latitudes several hours in advance. The operational implementation of STIM can support ionospheric forecasting space weather services and is based on the availability of real-time IMF observations from the vantage L1 point.