Modern society, industry and science increasingly rely upon space-based technologies, one of the main being GNSS (global navigation satellite systems). GNSS-based technologies and services are widely utilized: civil aviation uses GNSS-based navigation both during flights and for assisted landing procedures, smart farming increasingly relies on unmanned agriculture vehicles with GNSS positioning, and the general population routinely uses GNSS-based positioning and navigation both inside city limits and for long-range travels.

Ionosphere and its variability is one of the main natural sources of malfunctioning for the GNSS services. The ionosphere is an ionised layer of the upper atmosphere and its variability is driven by both internal and external forcings. The internal forcing is the neutral atmosphere dynamics (intrinsic waves and tides, atmospheric gravity waves generated by hurricanes, solar eclipses and other events, etc.). The external forcing is the space weather—conditions in the near-Earth environment driven by the Sun and its activity (e.g., solar flares or geomagnetic storms).

About a decade ago it was widely perceived that ionospheric variations at middle latitudes, being much smaller than the ones observed at high or equatorial latitudes, do not pose significant danger to GNSS-based technologies. However, continuous improvement in the sensitivity of GNSS instruments and their increasing abundance resulted in a growing concern of GNSS users in southwestern Europe about deterioration of the quality of the GNSS signal due to the ionospheric disturbances. To answer this concern a number of studies were performed by me and my team during the last 5 years focusing on the Portuguese regions and the needs of Portuguese GNSS users. These studies were focused on the ionospheric disturbances that last for up to a couple of days (such as the ones caused by geomagnetic storms). Several products designed to forecast ionospheric disturbances or to alert the GNSS users about potentially dangerous conditions were proposed or already developed as prototypes.

Here I present a project which aims to assess a specific type of ionospheric variability that also can deteriorate the quality of GNSS services, the short-term (from minutes to several hours) ionospheric variations associated with the atmospheric waves generated during space weather and atmospheric events. These short-term disturbances are difficult to analyze due to the high spatial and temporal resolution requirement on the ionospheric data. Only recently such data have become available with the introduction of a new generation of GNSS receivers and a significant growth of the receiver’s network. These technological advances make it possible to collect the ionospheric data with high resolution which, in turn, enables me to conduct the study of the short-term ionospheric variations outlined in this proposal.