Fluxgate magnetometers provide magnetic field measurements for geophysics and space physics. A low-noise ferromagnetic ring core typically determines the noise performance of the instrument. Much of the basic research into producing low-noise fluxgate sensors was completed in the 1960s for military purposes and was never publicly released. We present a manufacturing approach that can consistently produce fluxgate ring cores with a noise performance comparable to the legacy ring cores used today.

The comparison of geomagnetic active and quite events of double substorm onsets responsive to IMF variations shows that the occurrence sequence of all required substorm signatures looks the same and not different for small and large Kp. Double substorm onsets responsive to IMF variations can be characterized with two-stage magnetic dipolarizations in the magnetotail, two auroral breakups of which the first occurring at lower latitudes than the second, and two consecutive Pi2-Ps6 band pulsations.

We present a proof-of-concept space-flight instrument that can simultaneously make measurements of both the low- and high-frequency local magnetic field. Previously, this would have required two separate instruments that would normally have had to be mounted separately on long deployable booms to keep them from interfering. This new hybrid instrument is expected to be particularly useful on extremely small spacecraft, such as CubeSats, which can only accommodate a few instruments.

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.

Fluxgate magnetometers are an important geophysical tool but are typically sensitive to changes in sensor temperature. We used a novel, low-cost calibration procedure to compare six matched sensors in which the material used as the mechanical support is varied and found that 30 % glass-filled PEEK engineering plastic is a good candidate for sensors. It is more economical, easier to machine, lighter, and more robust than historically used machinable ceramic.

Based on the methods of critical fluctuations and natural time, we have shown that the fracture-induced MHz electromagnetic emissions recorded by two stations in our network prior to two recent significant earthquakes that occurred in Cephalonia present criticality characteristics, implying that they emerge from a system in critical state.

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.

Solar wind impacts the Earth’s magnetic cavity driving waves in the magnetosphere. The waves in the range of few mHz are important for the dynamics of energetic particles trapped inside the magnetosphere. The average solar wind parameters are known to control of magnetospheric wave power. Here the variability of solar wind parameters, rather than average properties, is analysed. It is shown that the magnetospheric wave power is most sensitive to variations in the interplanetary magnetic field.