The awe-inspiring night skies we enjoyed last month when a powerful solar storm struck have a more sinister side. It’s time we planned for the potentially deadly outcomes. Photo / Getty Images
From the archives: This week, you might have been hearing a fair bit about space weather - events beyond our atmosphere - solar storms and the likelihood of them wreaking havoc on Earth. Earlier this year, Eric Trump asked what the impacts of unsettled weather out to space can have on Earth.
‘What is the Sun?” asks Wes Magee. From this British poet’s perspective, it’s an “orange dinghy/sailing across a calm sea … a gold coin/dropped down a drain in Heaven … a yellow beach ball/kicked high into the summer sky … a red thumb-print/on a sheet of pale blue paper … a milk bottle’s gold top/floating in a puddle”.
From a less metaphorical view, the sun is a G-type yellow dwarf main sequence star halfway through its 10-billion-year life. Compared with other stars, such as Orion’s red supergiant Betelgeuse, the sun is middling in size, but for us, it ranks as a cyclopean presence, representing 99.8% of the total mass of the solar system. That includes all the planets, moons, asteroids, comets, Tesla Roadsters and whatever else is out there. We are just dust motes dancing in the sun’s glow.
The heliosphere, the sun’s magnetic atmosphere, cocoons the entire solar system, protecting it from interstellar radiation. Like a hula dancer, the sun spins faster at its equator than at its poles – and faster inside than outside. Its core is a thermo-nuclear furnace, where the pressure is more than one million tonnes per square centimetre, and every second, 609 million tonnes of hydrogen are converted through fusion into 605 million tonnes of helium, named for the Greek sun god, Helios.
The energy resulting from that elemental conversion takes 100,000 years to rise from the sun’s core to its surface. After that, it blasts off and reaches our eyes in eight minutes and 20 seconds.
Although the sun is 150 million kilometres away, it bathes us in its solar wind. This “wind” is actually plasma, the fourth state of matter (after solid, liquid and gas). Plasma is hot, electrically charged gas made up of mostly protons and electrons. It’s also what the sun is made of, not fire (fire is a chemical reaction between oxygen and carbon). If you imagine Earth as a rock in a stream, solar wind is the really fast, hot current flowing around it. This is the same current that makes a comet’s tail point away from the sun, whether it’s coming or going.
Since solar wind travels along the sun’s magnetic field lines, it would whisk away our atmosphere and turn us into Mars if not for the magnetic envelope, or magnetosphere, that protects us, curving out into space and converging near the North and South poles. The sun’s magnetic field is about twice as strong as ours, so solar wind squashes the magnetosphere on its sun-facing side and stretches it out on the night side into a long “magnetotail”.
For three days starting on May 10, we saw what happens when this stream of solar wind turns into a torrent. Our skies were lit up with the largest solar outburst in 20 years, as the sun lobbed extra plasma our way. The magnetosphere siphoned off the electrons and protons rushing past and deposited them like pennies into piggy banks at the North and South poles. Auroral inks stained the night sky green and red where solar particles collided with our atmosphere’s oxygen, and blue and violet where they hit nitrogen.
Solar activity waxes and wanes every 11 years. We are currently in what is known as a solar maximum, when the sun is at its most restless. The present cycle began in about 2019 and is expected to peak between now and 2025 (so keep looking up). During a maximum phase, the sun ejects more of its plasma more frequently. This happens because the sun’s unstable magnetic field lines twist and tangle, especially in dark areas on its surface called sunspots.
Magnetic energy builds up, reaches a breaking point and “snaps”, causing the sun to geyser and belt out electromagnetic radiation in the form of solar flares and giant blobs of magnetised plasma called coronal mass ejections, or CMEs. A solar flare cannot be prepared for because it reaches us in eight minutes. CMEs take longer, usually about a day and a half.