The massive solar flare that caused yesterday’s geomagnetic storm disabled satellites, knocked out internet routers, and caused blackouts in many regions, as transformers tripped, and power surges ripped through utility grids. The tsunami of charged particles striking the Earth’s magnetic field generated electrical charges in unshielded electronic equipment, and powerful currents in overhead cables.

Scientists have long been worried about a major event like this. It seems that alternating current (AC) transmission lines are particularly susceptible as the frequency is disrupted by magnetic waves, causing huge fluctuations in power. Think of it like the magnetic induction we use to wirelessly charge our devices, but on a cosmic scale. The resulting current dips and spikes can cause substation transformers to fail or even explode.

But direct current (DC) equipment is more resilient. In recent years the solar power revolution has spawned a need to link solar farms in sunny places to distant consumers with gloomy weather. High voltage DC cables were developed to do this with high efficiency, even over thousands of kilometres, allowing developing countries with an abundance of sunshine to become major energy exporters.

These heavy DC cables are mainly installed as underground or submarine interlinks, shielding them from geomagnetic disturbance and maintaining stable power capacity. They operate like pipelines, but for electricity, not gas, even capable of two-way traffic for the efficient sharing of power between countries. As solar continues to grow exponentially, so does this ‘global grid’.

And that’s what saved us from a potential global catastrophe during the solar storm. Satellite communications might be down, but thanks to fiber optics and direct current, we have managed to stay online – and keep the lights on.