Solar Flares and Solar Energetic Particles emitted by the Sun’s ‘solar storms’ may cause severe radio interference on Earth and endanger astronauts and spacecraft, but the most dangerous part of a ‘solar storm’ for Earthlings is a Coronal Mass Ejection, (CME) – which occurs when magnetic reconnection on the Sun’s surface “pinches off” a giant loop of magnetic field, blasting off a big chunk of the Sun’s super-hot plasma.
The first Coronal Mass Ejection (CME) observed by humankind was the Carrington Event in 1859, when a huge fast moving CME struck Earth in just 17 hours after a solar flare – distorting Earth’s magnetic field and creating a massive magnetic storm across the globe.
The resulting Auroras filled the sky in spectacular fashion, with the Aurora Borealis being visible as far south as the Caribbean and sub-Saharan Africa, while the Auroras were so bright in the northern USA that some people mistook them for the dawn light and began preparing breakfast!
More ominously, the huge magnetic disturbance induced strong electrical surges and sparks in the telegraph systems that spanned Europe and North America, disrupting humanity’s equivalent to the ‘Internet’ at the time.
It’s these induced electrical currents created by CMEs hitting Earth that makes them such a great threat to our highly electrified civilization today. In 1989 a smaller magnetic storm knocked out power across most of Quebec, but as inconvenient as that was, it’s small potatoes compared to the damage another ‘Carrington-class’ CME could do to us.
Photo: 2012 CME as seen by NASA’s Solar Dynamics Observatory (SDO)
Credit: NASA (public domain)
In the summer of 2012 there was another giant ‘Carrington-class’ solar ‘superstorm’ – luckily when the huge CME blasted across the path of Earth’s orbit our planet was a few days further along, so we were well out of the way.
If that CME had struck Earth the magnetic storm and induced electrical surges would have destroyed vital power transmission grids and transformers, and would have wrecked electrical & electronic equipment across the world, doing an estimated $2Trillion of damage – knocking civilization back decades.
What’s more, one physicist estimated there’s a 12% chance of another huge ‘Carrington-class’ CME like this hitting the Earth in the next ten years!
Worse still, the 2012 CME was actually a ‘double whammy’ of two CMEs travelling 10 to 15minutes apart. New work from researchers at the University of Reading in the UK may help explain why such ‘one-two-punch’ CMEs occur.
According to Professor Mathew Owens: “Up until now, it has been assumed CMEs move like bubbles through space, and respond to forces as single objects. We have found they are more like an expanding dust cloud or sneeze, made up of individual plasma parcels all doing their own thing.”
Basically, scientists found that CMEs expand so quickly that they soon stop being a singular coherent structure. So, one or other part of the CME cloud can be distorted by external forces without affecting the rest of the cloud. External forces include: the braking forces generated as a fast CME ploughs its way through the spiral magnetic fields of the interplanetary solar wind.
Image: Visualisation of the heliospheric current sheet – the spiral surface where the magnetic field of the Sun / interplanetary solar wind switches its polarity from N-S.
Credit: NASA/Werner Heil via Wikimedia (public domain)
The cloud-like nature of CMEs makes trying to predict their shape and movement as they plough through the solar wind extremely difficult. Perhaps, if the solar wind varies strongly enough it’s possible that it could tear one CME cloud apart into two! Clearly, we need a much more thorough understanding of the solar wind.
We do know that when the Sun moves into the quieter, less active half of its 11 year cycle, then the interplanetary solar wind gets thinner and weaker – so it has less of a braking effect on fast moving CMEs. So, even though CMEs happen about 17 times less often in this quieter part of the solar cycle – if the Sun does sneeze out a huge CME in the direction of Earth, it would hit us faster and harder, inducing stronger magnetic storms, and wreaking greater destruction on our electrical technology.
We’re currently about nine and half years deep into Solar Cycle 24, dropping into the minimum period of solar activity. However, most of Cycle 24 has been unusually low in activity – in fact it’s shown the lowest activity since accurate records began around the year 1750.
Scientists at the University of Reading predict that by around 2050 the Sun’s overall activity will drop to the kind of ‘grand minimum’ that we’ve not seen since the 70 year-long ‘Maunder minimum’ which was way back in the 17th Century. That would mean a thinner, weaker solar wind lasting for decades!
There is some good news: right now humanity has the best early warning systems monitoring the Sun in history – there’s a whole fleet of spacecraft dedicated to solar monitoring, with no less than four (SOHO, WIND, ACE & DSCOVR; operated variously by NASA, ESA and NOAA) in orbit directly between the Earth and the Sun – providing data on any incoming solar space weather before it hits Earth, indeed yielding enough data that US Federal agencies NOAA & NWS can provide real-time online Space Weather forecasts to the public.
Also, some governments and corporations are waking up to the danger of solar storms, and are starting to take some action to reduce the predicted disruption of electrical infrastructure – although there’s still a lot of work to be done before humanity is really ready to ride out another ‘Carrington Event’, without it suddenly throwing us back about 100years, technologically speaking.
Sources for quotes by & paraphrases of University of Reading scientists:
Source for some of the info re. 2012 CME: