Aurora delayed, massive solar flare erupts from the Sun

Thursday, 7 September 2017

A massive solar flare overnight could mean a stunning aurora is on the way.

An aurora failed to show up in New Zealand skies overnight Wednesday, but it could still be on the way, and has received a boost from the largest solar flare in over a decade.

The solar flare was unleashed around midnight (NZT), Spaceweather.com reported. 'X-rays and UV radiation from the blast ionised the top of Earth's atmosphere, causing a strong shortwave radio blackout over Europe, Africa and the Atlantic Ocean.'

The explosion produced a coronal mass ejection. Analysts at the US National Oceanic and Atmospheric Administration (NOAA) were modelling the trajectory of the CME on Thursday morning to determine whether it was headed towards the Earth.

CMEs are huge explosions of magnetic field and plasma from the Sun's corona. If they impact the Earth they can cause geomagnetic storms and particularly strong auroras.

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The solar flare overnight ranked as the 14th strongest recorded since 1976. It was relatively mild compared to the Halloween storms of 2003, Spaceweather.com said.

'Modern power grids, telecommunications, and other sun sensitive technologies should weather the storm with little difficulty. On the other hand, sky watchers could see some fantastic auroras before the week is over. And ham radio operators will surely be noticing strange propagation effects as the sun exerts its influence on our planet's ionosphere.'

Otago Museum director Dr Ian Griffin said the material that it had been thought might arrive at the Earth overnight Wednesday was 'running a bit late'.

But with the new material added from the large solar flare chances were there would be a good aurora display during the 24 - 48 hours from Thursday morning. Auroras were a natural phenomenon and hard to predict.

Uncertainties included when the material from the Sun was due to arrive at the Earth, how strongly it would interact with the Earth's atmosphere, and what time of day it arrived.

It could arrive during the day in New Zealand, but if it did get here overnight Thursday, the forecast suggested skies would be clearer than they were last night, Griffin said.

'Almost certainly something will be seen in the South Island. I don't know how bright,' he said.

'If it's really powerful, potentially you could see it in Wellington or even further north, but it's really hard to predict auroras.'

While prediction was difficult, 'a number of people are really excited about what's heading in our direction'.

MetService cautioned the Moon would be 99.9 per cent full overnight Thursday, which was 'not ideal for aurora spotting'.