Solar extravaganza: Auroras put on fantastic light show for East Coasters

The district’s power supply came under threat from the power of the sun over the weekend, while spectacular auroras lit up night skies from one end of New Zealand to the other. 

Auroras were seen as far north as Auckland and Northland, while here, only parts of the coast north of Gisborne were free from cloud cover, allowing people to enjoy the sight. 

The sun is approaching a peak in an 11-year cycle of activity, with huge magnetic fields entangling like rubber bands hundred of thousands or millions of kilometres long. When the magnetic fields become too knotted, they can burst with a “snap” that hurls millions of tonnes of highly charged matter into space. 

The dark areas on the sun, known as sunspots, are where the magnetic fields become “knotted”. As the sun rotates, those dark areas can point directly at Earth and if there’s an eruption, hurl vast clouds of protons and electrons at us. When those particles hit Earth’s own magnetic field (the magnetosphere), the interaction causes colourful auroras — most often near the North and South Poles. 

Over the weekend, a series of eruptions occurred on the sun, the strongest since 2005. 

As well as causing auroras, solar flares and coronal mass ejections (CMEs) are a major worry because they can pose a serious threat to power supplies, satellites and telecommunications systems. 

The huge electric charge carried in a CME can “latch” on to electrical systems through a process known as induction. High-voltage power lines create their own magnetic fields and can “attract” the incoming solar blast. 

This happened in 1859 during the Carrington Event, when telegraph lines across America became highly charged, caused fires and destroyed telegraphic offices and gear. 

At the weekend, Transpower, on advice from US space agencies, acted to protect New Zealand’s power supply network by shutting down parts considered vulnerable. 

A Transpower spokesman told the Gisborne Herald the main threat was to the north-south high voltage lines linking the country from end to end. 

Extra consideration was also given to ensuring power was maintained in more isolated areas such as the Gisborne-East Cape region, where supply is from lines from Tuai at Waikaremoana. 

Sections of line were shut down in the South and North Islands. 

Over the weekend, dozens of solar outbursts occurred, with four in the most powerful X-flare category. 

At its worst, the solar flux was rated KP9 and the geomagnetic storm as G5 - the highest ratings on the scale. 

Transpower’s emergency action and alerts started on Saturday and were extended twice through to Monday, when the solar situation finally eased. 

Most of the flares and CMEs came from a sunspot numbered AR3664 — an area spanning a mind-boggling 200,000km, or the equivalent of up to 15 Earths side by side. 

As well as posing a threat to electric grids and power transmission, outbursts from the sun can disrupt radio and TV communications, and over the past few days there have been quite a few radio blackouts around the world. 

Fortunately, New Zealand is less exposed to the solar threat because at this time of year, the planet’s orbit means the Southern Hemisphere is tilting away from the sun.