A huge outburst on the sun has scored a "direct hit" on Earth, and could cause minor disruptions to power grids in northern latitudes.
The Space Weather Prediction Center, part of the US National Oceanic and Atmospheric Administration, issued a geomagnetic storm warning on Sunday for Monday and Tuesday.
The warning suggested the storm could affect power grids in some areas, and satellites, but in practice these effects are likely to be minor.
The Australian Bureau of Meteorology's Space Weather Service [SWS] said the Earth is "is currently under the influence of a full-halo CME triggered by a M1.6 flare" and auroras may be visible if geometric storms continue through the night.
The SWS said the coronal mass ejection (CME) arrived on October 11 at around 5pm universal time (UT), which is about a 4am on October 12 AEDT.
"On the local night of 11 October (and maybe 12 October), aurora may be visible from Tasmania, the coastline of Victoria and the southwest coast of Western Australia," the Space Weather Service said.
The Space Weather Service said solar activity was low on October 11, UT, and only B-class flares were observed, but there is a chance C-class flares could be seen in the coming days.
The aurora could also be visible in some parts of the UK, the Met Office said.
"On the 11 October a coronal mass ejection is expected to arrive at Earth, with minor to moderate geomagnetic storms likely, resulting in enhanced auroral activity during 11 October," The Met Office said.
"There is a slight chance of aurora reaching the far north of England and Northern Ireland tonight, but cloud breaks and therefore sightings are more likely in Northern Ireland.
"Minor storms may continue into 12 October, before a fast wind from a coronal hole may arrive, perhaps continuing the rather active period of geomagnetic activity."
We are awaiting the impact of a coronal mass ejection launched by an M1.6 solar flare that took place two days ago.
The impact is expected to occur within the next 12 hours. A moderate G2 (Kp6) geomagnetic storm watch is in effect.
Follow it live on https://t.co/XHATH0OOfT pic.twitter.com/U9myFrgOrG
— SpaceWeatherLive (@_SpaceWeather_) October 11, 2021
Coronal mass ejections are large clouds of solar plasma and magnetic fields released into space after a solar eruption.
Stretching over millions of miles, they can cause northern lights when they hit Earth’s atmosphere.
Solar storms are ranked from G1 to G5, with stronger storms having the potential to cause radio blackouts.
This week’s storm will be at the lower end of the scale, the Met Office said.
It added that aurora could continue into the week, saying: “Aurora is possible through 11th and 12th across much of Scotland, although cloud amounts are increasing, meaning sightings are unlikely for most.
NASA describes a geomagnetic storm as an interaction in Earth’s magnetosphere.
“When a coronal mass ejection or high-speed stream arrives at Earth it buffets the magnetosphere," NASA said.
“If the arriving solar magnetic field is directed southward it interacts strongly with the oppositely oriented magnetic field of the Earth.
“The Earth's magnetic field is then peeled open like an onion allowing energetic solar wind particles to stream down the field lines to hit the atmosphere over the poles.”
— Rob Waugh, Yahoo UK
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