The emergency response agency is preparing for power and communications outages in the event of an extreme solar storm.

New Zealand's National Emergency Management Agency has released an interim response plan for space weather in August, and said it planned to update that in the coming weeks.

Space weather refers to events beyond Earth's atmosphere. The primary source is the sun, with disturbances coming in the form of solar flares, coronal mass ejections and magnetic storms.

Scientists from NASA, the National Oceanic and Atmospheric Administration and the international Solar Cycle Prediction Panel announced in mid-October that the 11-yearly peak in the sun's activity known as the solar maximum was well under way, which increased the chance of solar flares.

While the flares do not pose a direct risk to human health, they can mess with electricity production, communication and navigation equipment crucial to society.

NEMA's interim response plan said extreme space weather was a "low probability event", but had "the potential for far reaching, and potentially catastrophic consequences" and "may disrupt, damage, or cause the loss of critical infrastructure".

The interim plan was designed to guide the response in the event the country loses power, satellite communications, GPS, radio and telecommunication systems.

It does not cover longer-term effects, such as health impacts or corrosion of fuel pipelines, re-entry of space debris resulting from space weather, or malicious threats.

The minister for emergency management and recovery (currently Mark Mitchell) would be the lead minister, tasked with keeping Cabinet informed of developments and deciding whether to declare a State of National Emergency.

NEMA would be tasked with receiving international alerts for imminent space weather events, coordinating public messaging, and using alternative communication methods if the solar storm took out the usual channels.

The country would enter alert mode when NEMA received a notification of anything at or higher than a level three geomagnetic storm, a level four solar storm, or a level four radio blackout, and the plan would be activated when a significant space weather event was "imminent and [the] geographic location has been confirmed".

What is a solar storm, anyway?

Dr Malcolm Ingham, from Victoria University of Wellington, said that the sun was constantly emitting material - like protons and electrons - from its surface into space. This was called solar wind.

The sun's activity peaked about every 11 years, meaning intense magnetic fields, and periodically, there were emissions of electromagnetic radiation, called solar flares, or big ejections of plasma from the outer surface, called coronal mass ejections.

"If a coronal mass ejection or an intensity in solar wind hits the earth, that's what we would refer to... as the effects of a solar storm," Ingham said.

"Under the right circumstances it gets into the Earth's magnetic field, into our atmosphere, a few hundred kilometres above the surface of the Earth, called the ionospere."

That manifested as a beautiful and harmless aurora - but intense events could present a hazard to satellites, and affect GPS and navigation equipment.

Ingham said there was usually a day's warning at most.

In May, when auroras were visible even from parts of the North Island, planes across the Atlantic were rerouted because of the effects on GPS, and parts of the electricity grid were turned off to prevent overheating caused by interfering currents.

"Transformers don't sit on shelves," he said.

"If you lose a transformer, it's not easy to replace it at the drop of a hat. If you lose 10, you've got a long time before you can replace them."

Now, the sun was nearing the solar maximum. Ingham said the previous one wasn't very intense, but "this one is shaping up to be considerably stronger" - and the May event had given scientists good data.

"What we've had this year has actually been a boon, because it's actually given us something a lot bigger to work on."

National grid prepares for the next storm

Matt Copland, Transpower's head of grid and system operations, said Transpower had been working on how to manage these kinds of events for years, with the first plan put in place in 2010.

But the impending solar maximum had brought things back into the spotlight.

The worst-case scenario, Copland said, was that currents caused by coronal mass ejections could cause overheating in Transpower's equipment, or mess up protection systems - and despite having a number of spare parts, in the event of a global event, those would be in hot demand and take longer to replace.

To avoid that, the plan for such an event involved switching off parts of the power system until it was over, which could take up to 36 hours.

Multiple transmission circuits (transmission lines between substations) were taken offline on 11 May during solar storm Gannon, in a way which meant no impact on consumer supply.

How much damage could a large event do?

Aside from the disruption to people and businesses relying on power, communications and GPS, the damage to infrastructure from fried systems could cost a lot.

Research in the United States estimated the damage costing up to US$2.7 trillion (NZ$4.6 trillion), and New Zealand's Ministry of Business, Innovation and Employment said a very rough estimate put this country's annualised risk at $1 billion a year.

It funded the University of Otago's Solar Tsunamis project in 2020 to the tune of $15 million over five years.

-RNZ.