Abstract. The temporal and spatial behaviour of the ionospheric parameters foF2 and h F during isolated substorms are examined using data from ionospheric stations distributed across Europe and western Asia. The main purpose is finding the forerunners of the substorm disturbances and a possible prediction of these disturbances. During the period from March 1998 to March 1999, 41 isolated substorms with intensities I = 60 − 400 nT were identified and studied. The study separated occasions when the local magnetometers were affected by the eastward electrojet (positive substorms) from those influenced by the westward electrojet (negative substorms). The deviations of the ionospheric parameters from their monthly medians ( foF2 and h F) have been used to determine the variations through the substorm. Substorm effects occurred simultaneously (< 1 h) across the entire observatory network. For negative substorms, foF2-values increase > 6 h before substorm onset, T o , reaching a maximum 2-3 h before T o . A second maximum occurs 1-2 h after the end of the substorm. The h F values 3-4 h before T o have a small minimum but then increase to a maximum at T o . There is a second maximum at the end of the expansion phase before δh F drops to a minimum 2-3 h after ending the expansion phase. For positive substorms, the timing of the first maximum of the δfoF2 and δh F values depends on the substorm length -if it is longer, the position is closer to T o . The effects on the ionosphere are significant: foF2 and h F reach 2-3 MHz (δfoF2 = 50-70% from median value) and 50-70 km (δ h F = 20-30% from median value), respectively. Regular patterns of occurrence ahead of the first substorm signature on the magnetometer offer an excellent possibility to improve short-term forecasting of radio wave propagation conditions.
Abstract. Satellite telecommunications, positioning and navigation systems require knowledge of the electron distribution in height Ne(h) to high-altitude orbits of satellites. One of the possibilities to construct such profiles is associated with the use of the ionospheric total electron content TEC. This paper is devoted to three advantages of the IRIPlas model. They include introduction of the topside basis scale height Hsc, expansion of the IRI model to the plasmasphere, ingestion of experimental values of TEC. Testing of this model according to different satellite experiments (CHAMP, DMSP) shows the high efficiency of this model. The method of adaptation of the IRI-Plas model to the plasma frequency at altitudes of CHAMP and DMSP satellites allows us to produce behavior of Ne(h)-profiles during the disturbances, as well as to refine the values of TEC, which determine the accuracy of positioning. Results were obtained using data of the European area.
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