Swarm is the fourth Earth Explorer mission of the European Space Agency (ESA), launched on 23 November 2013. The mission provides an opportunity for better knowledge of the near-Earth electromagnetic environment. This study presents an initial attempt to derive an ultra low-frequency (ULF) wave index from low-Earth orbit satellite data. The technique can be potentially used to define a new product from the mission, the Swarm ULF wave index, which would be suitable for space weather applications.

Our study demonstrates a remarkable association between the earthward penetration of ULF waves and radiation belt electron enhancements during four magnetic storms that occurred in 2001. In the past, ULF waves had been observed at unusual depths during rare superstorms. But ULF wave activity, reaching magnetic shells as low as 2, was also observed during relatively intense storms when it played a key role in diffusing electrons radially inward and thereby accelerating them to higher energies.

A number of current systems exist in the Earth's magnetosphere. It is very difficult to identify local measurements as belonging to a specific current system. Therefore, there are different definitions of supposedly the same current, leading to unnecessary controversy. This study presents a robust collection of these definitions of current systems in geospace, particularly in the near-Earth nightside magnetosphere, as viewed from a variety of observational and computational analysis techniques.