As computing and geophysical sensor components have become increasingly affordable over the past decade, it is now possible to design and build a cost-effective system for monitoring the Earth's natural magnetic field variations, in particular for space weather events.

Modern fluxgate magnetometers are sensitive down to the sub-nanoTesla (nT) level, which far exceeds the level of accuracy required to detect very small variations of the external magnetic field. When the popular Raspberry Pi single-board computer is combined with a suitable digitiser it can be used as a low-cost data logger. We adapted off-the-shelf components to design a magnetometer system for schools and developed bespoke Python software to build a network of low-cost magnetometers across the UK.

We describe the system and software and how it was deployed to schools around the UK. We show the results recorded by the systems from September 2017, one of the largest geomagnetic storms of the current solar cycle.