Intense disturbances in the ionosphere may produce perturbations in Global Navigation Satellite Systems (GNSS) radio signals that in the most severe cases produce receiver tracking problems, which in turn impact on GNSS positioning accuracy. In this paper we present a case study related to the sudden increase in total electron content (SITEC) induced by the X17.2 solar flare that occurred on 28 October 2003. This is the largest SITEC ever recorded by means of the rate of change of total electron content. A solar radio burst (SRB) occurred in the same period which caused GNSS signal fading and in some cases complete signal loss. Although SITEC contribution to the signal noise cannot be separated from that of SRB, in this paper we show that accuracy degradation may happen in kinematic precise point positioning (PPP) in several stations of the sunlit hemisphere when 30 s sampling rate data are analyzed. The observed errors in the position are the result of the difficulties that cycle slip (CS) detection strategies have to deal with the observables that have been affected by the SITEC.

Midlatitude locations are unique regions exposed to both geomagnetic storm and substorm effects, which may be superposed on specific events imposing an extra handicap for the analysis and identification of the sources and triggers. We study space weather effects at the midlatitude location of the Iberian Peninsula for the St. Patrick's day events in 2013 and 2015. We have been able to identify and separate storm and substorm effects on ground magnetometer data from San Pablo‐Toledo observatory during storm time revealing important contributions of the Substorm Current Wedge on both events. The analysis of these substorm local signatures have shown to be related to the production of effective geomagnetically induced currents and ionospheric disturbances as measured from Global Navigation Satellite Systems data at MAD2 IGS permanent station and not directly related to the storm main phase. The whole Sun‐to‐Earth chain has been analyzed in order to identify the solar and interplanetary triggers. In both events a high‐speed stream (HSS) and a coronal mass ejections (CME) are involved, though for 2015 event, the HSS has merged with the CME, increasing the storm geoeffectiveness. The enhancement of substorm geoeffectiveness is justified by the effects of the inclined magnetic axes of the Sun and of the Earth during equinox period.

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