Global · Space Weather
Coronal Mass Ejection
ElevatedA massive eruption of solar plasma striking Earth's magnetic field and inducing destructive currents in power grids.
- Likelihood
- ~1-2% per decade for a Carrington-class event
- Impact
- Civilisation-changing; multi-month grid outage
- Horizon
- Any time; peaks around solar maximum
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Background
What this actually is
A coronal mass ejection is billions of tonnes of magnetised plasma thrown off the Sun. If it hits Earth it compresses the magnetosphere and induces geomagnetically induced currents in any long conductor — transmission lines, pipelines, rail signalling, undersea cables.
The 1859 Carrington event set telegraph offices on fire. The 1989 Québec storm blacked out six million people in 90 seconds. A Carrington-scale event today would damage extra-high-voltage transformers, which are custom-built, weigh hundreds of tonnes, and have lead times measured in years.
Warning time is 15 hours to 3 days from eruption to arrival, which is enough to protect a grid if operators act. That is the single most important fact about this threat: it is preventable with preparation, unlike most on this list.
Aotearoa
What it means for New Zealand
New Zealand's long transmission lines and high ground resistivity make it more exposed than its latitude suggests. Transpower has a geomagnetic disturbance response plan and has recorded significant induced currents during past storms — the May 2024 Gannon storm caused a transformer failure at Islington. NZ manufactures no high-voltage transformers.
Watch for
Early warning signs
- NOAA SWPC G4/G5 geomagnetic storm watches
- Planetary K-index above 7
- Aurora visible far outside its normal latitude band
- Transpower or lines companies announcing protective load reduction
Action
How to prepare
- 01
Plan for weeks without mains power, not hours — that is the distinguishing feature of this event
- 02
Water is the first failure: pumping stops when power does. Store 3+ litres per person per day
- 03
Keep a non-electronic way to cook and stay warm
- 04
Cash, paper records and a battery radio; EFTPOS and mobile networks fail early
Go deeper
Where to find more information
In an emergency
New Zealand's official channels
- Get Ready — household preparedness
- Civil Defence / NEMA
- GeoNet — quakes, volcanoes, tsunami
- MetService severe weather warnings
In a life-threatening emergency call 111. RNZ National is New Zealand's designated lifeline broadcaster — keep a battery radio.
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