A study published in Space Weather argues that geomagnetic storms can threaten electricity networks through sustained geomagnetically induced currents, not only through brief current spikes. The finding matters for critical infrastructure resilience because prolonged current flow can heat transformers, saturate magnetic cores, and increase wear on grid equipment.
What happened
The study examined the June 2015 severe storm over New Zealand. The researchers report that the event did not mainly produce a sharp surge in grid currents. Instead, it sustained geomagnetically induced currents for about 90 minutes.
The authors say even a current of roughly 20 amperes can be harmful if it persists long enough. Their explanation is that sustained currents can heat transformers and stress magnetic cores as those cores saturate.
Why the study changes the risk picture
The study argues that storm-risk assessment must look beyond sudden spikes. It must also account for long-duration current effects, local ground conductivity, and transmission-line layout. In other words, the same storm can create different levels of risk in different places because the ground and the grid are not uniform.