Multi‐Instrument Approach to Study Polarization Jet/SAID and STEVE.

In this study, we employ a unique multi‐instrumental approach for a comprehensive examination of Polarization Jet (PJ) (or, another name, Subauroral Ion Drift (SAID)). A diverse set of data is used to assess the connection between the appearance of the inhomogeneous structure of PJ/SAID and its reflection in ground‐based observations during geomagnetic activity. Our approach combines satellite (Defense Meteorological Satellite Program, NorSat‐1, Swarm) and ground‐based (ionosondes, magnetometers, GPS/GLONASS receivers) data, allowing us to study PJ/SAID in detail and compare satellite data with ground‐based measurements. We describe the characteristic patterns on ionograms that may indicate the presence of PJ/SAID and how ionosondes can be used to study PJ/SAID. Polarization Jet Strata and irregularities of plasma parameters can cause multiple reflections, which are visible in ionograms as F‐spread. The splitting of the F2 trace into two or more traces on ionograms may indicate the presence of PJ/SAID near the observation point. Data from GPS/GLONASS receivers in regions where PJ/SAID is observed enable the construction of local total electron content maps, visualizing how PJ/SAID is reflected in those maps. It is shown how the geomagnetic latitude of PJ/SAID changes during the geomagnetic activity. Furthermore, this case is notable because not only PJ/SAID but also STEVE (Strong Thermal Emission Velocity Enhancement) is observed at subauroral latitudes in Northern Europe during the examined geomagnetic event. Plain Language Summary: Narrow and extended structure known as a polarization jet (PJ) or the sub‐auroral ion drift (SAID) is regularly observed in the subauroral region at the boundary of the auroral oval in the evening and night hours during geomagnetic activity. The PJ/SAID is a fast westward ion drift and is one of the main signatures of a geomagnetic disturbance in the ionosphere. On the one hand, this phenomenon is interesting from the point of view of fundamental physics, since there is still no generally accepted single point of view on the mechanisms that cause PJ/SAID. On the other hand, the decrease in the density of the ionospheric plasma within PJ/SAID substantially affects the conditions for the propagation of shortwave radio waves, which indicates the practical importance of studying PJ/SAID. This study uses a multi‐instrumental approach to study the properties of PJ/SAID by comparing various observations, including satellite ones. We explain how ionosondes, GPS/GLONASS receivers and magnetometers can serve as indicators of the presence of a PJ/SAID during geomagnetic disturbances using ground‐based data. The appearance and development of PJ/SAID are closely linked to the recently discovered optical phenomenon in the subauroral region known as STEVE, which is also observed. Key Points: Polarization Jet (PJ)/ Subauroral Ion Drift (SAID) is studied using a multi‐instrumental approach and detailed comparison of satellite and ground data is carried outIt is shown how PJ/SAID and STEVE manifests on traces on ionograms, magnetograms and local TEC mapsPJ Strata and small‐scale plasma irregularities can cause multiple reflections, which are visible in ionograms as F‐spread [ABSTRACT FROM AUTHOR]