The Earth’s magnetic field results from different sources: internal sources due to fluid motion in the Earth’s outer core and magnetized rocks in the lithosphere, and external sources due to electric currents in the ionosphere and magnetosphere.

Magnetic field observations taken at ground level and in space can be used to describe and interpret the various sources, e.g. regarding core field secular variation, solar–terrestrial interaction in near Earth space, and processes in the ionosphere. However, a meaningful investigation of the different processes requires their proper isolation in magnetic field observations.

This Workshop aims at describing the characteristics of the different magnetic field sources with the goal to isolate them properly in magnetic field observations and to discuss suitable approaches for source characterisation.

It will bring together experts on the Earth interior and on ionospheric and magnetospheric electric currents, including observations and modelling, to tackle these questions properly. The resulting book will summarize the outcome including research on problems that benefit from proper source characterisation in the magnetic field, such as:

• How to define “magnetic quiet conditions” in polar and non-polar regions? Which sources are present during magnetically quiet conditions and what is their character?

• What are recent modelling capabilities for predicting magnetic field contributions during magnetically inactive conditions?

• What is the uncertainty in specifying unwanted field contributions for a study of external currents?

Especially with the advent of multi- satellite missions and an increasing number of ground stations, this book will largely contribute to a better understanding if the different sources of the Earth magnetic field.