This paper presents an analysis of high-resolution optical and radar observations of a phenomenon called fragmented aurora-like emissions (FAEs) observed close to aurora in the high Arctic. The observations suggest that FAEs are not caused by high-energy electrons or protons entering the atmosphere along Earth's magnetic field and are, therefore, not aurora. The speeds of the FAEs and their internal dynamics were measured and used to evaluate theories for how the FAEs are produced.

During geomagnetic storms, enhanced solar wind and changes in the interplanetary magnetic field lead to ionisation anomalies across the polar regions. The superstorm of 20 November 2003 was one of the largest events in recent history. Numerical simulations of ionospheric dynamics during the storm are compared with plasma observations to understand the mechanisms forming the polar plasma anomalies. The results are important for understanding and forecasting space weather in polar regions.

Small-scale auroral features are still being discovered and are not well understood. Where aurorae are caused by particle precipitation, the newly reported fragmented aurora-like emissions (FAEs) seem to be locally generated in the ionosphere (hence, aurora-like). We analyse data from multiple instruments located near Longyearbyen to derive their main characteristics. They seem to occur as two types in a narrow altitude region (individually or in regularly spaced groups).

The boundary of regions with a plasma density much lower than background was investigated in the northern polar cap using observations of ionospheric plasma density. Similar regions with an above-background density have been linked to fluctuations in phase and amplitude in radio waves traversing the density gradient at their boundary. These fluctuations were absent through the gradient in the below-background regions; thus, a minimum of both density and gradient are required for scintillation.

The Earth's polar upper atmosphere changes along with the magnetic field, other parts of the atmosphere, and the Sun. When studying these changes, knowing the polar region that the data come from is vital, as different processes dominate the area where the aurora is and poleward of the aurora (the polar cap). The boundary between these areas is hard to find, so this study used a different boundary and figured out how they are related. Future studies can now find their polar region more easily.