Transpower has issued a grid emergency notice as a precaution ahead of the largest solar storm in decades likely to affect Earth this weekend.
Eight South Island transmission lines and one transformer were to be removed from service today, including in Gore, Twizel, and Roxburgh.
Transpower said in a statement: "As part of our contingency plan we are removing some transmission lines from service across the South Island as a precaution. In order to do this, we have to issue a grid emergency notice, however this initial action should not impact supply of electricity to consumers."
The severity of the geomagnetic storm, classified as a G4, that sent multiple solar flares toward Earth could impact the power grid, radio signals, and satellite and communications systems, the US National Oceanic and Atmospheric Administration (NOAA) said.
"G4 [severe] level events are rare, with only three having been observed this solar cycle since December 2019. Our control rooms are monitoring the event," said a Transpower spokesperson.
The NOAA said a large sunspot cluster has produced several "moderate to strong" solar flares since Wednesday. Solar flares are eruptions of electromagnetic radiation in the Sun's atmosphere.
At least five coronal mass ejections of varying intensity and consisting of electromagnetic gas are expected to arrive at Earth over the next two days, prompting the first severe geomagnetic storm watch since 2005.
The solar storm emanates from a large sunspot cluster 16 times the diameter of Earth. A sunspot is a visibly darker region of the Sun's surface where surface temperature reduces due to high magnetic pressure.
The most recent event of similar or greater magnitude occurred in October 2003. That was a G5 level solar storm that wreaked havoc with power globally, notably in Sweden and South Africa where power outages occurred and transformers were destroyed.
The most intense event on record occurred in September 1859, known as the Carrington Event.
Aurorae were seen as close to the equator as Mexico and Hawaii and telegraph systems failed across North America and Europe, in some cases giving their operators electric shocks.
A storm of this magnitude occurring today would cause widespread electrical disruptions and blackouts worldwide.
Aurora over Geraldine, Canterbury. (Source: Supplied)
The solar storm also brings a bonus for Kiwi skywatchers: "Vivid" auroras visible as far north as Nelson.
Astronomer Rob Davison told 1News that New Zealand could be in for some good aurorae over the weekend.
"Based on forecasts, the material is likely to arrive here sometime on Saturday, with the best chances for aurorae visible from New Zealand likely to be overnight from May 11 to May 12."
He said there were a few key things to remember for anyone hoping to catch a glimpse of an aurora.
"Increased solar activity improves the chances of a good auroral display, but it does not guarantee it.
"Aurorae can also peak and then disappear in a relatively short amount of time.
"Getting as far south and as far away from light pollution as possible will improve your chances.
"People should also remember to wrap up warm, as they may need to be outside for some time while their eyes adjust to the dark and while they wait for the peak of any display to appear."
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