If Earth's communication is hit in coming days, blame the sun

Like most stars, the sun has a mercurial temperament. There are periods when it is (relatively) quiet and those when it sees sharp increases in activity. Oddly enough, the more advances we make technologically, the more vulnerable we are to the sun’s moods.

The next few days will see a certain amount of stress-testing for the world’s satellites and hence, our communication and geo-location systems could be affected as the sun is going through a stormy period.

On March 13, a large solar flare was released, and it travelled towards Earth at around 600 km per second. It led to a relatively minor storm.

There are several more solar storm alerts for the next several days. Two solar flares hit on Tuesday and more are expected to arrive late on Wednesday night (IST) and through Thursday. A single Coronal Mass Ejection (CME) can cause disruptions over several hours. (CMEs are like spherical storms, which are 20 million km in radius.)

And so, astronauts won’t be taking spacewalks for a while due to high radiation effects. If the storms are major, they could disrupt power grids, fry satellites, and put high-accuracy GPS systems out of whack.

While solar flares are known to occur around March every year, CME is not a simple solar flare. And this time round, there are more of them, and bigger ones, putting more satellites at risk. Last month, for instance, a solar storm destroyed 40 of 49 Starlink satellites newly launched by SpaceX CEO Elon Musk.

Why do solar storms happen and what do they do?

Stars create energy by crunching atoms together until they fuse, turning into different elements and releasing excess particles that are converted into energy. This happens on a gigantic scale. The sun is a relatively small star and it still contains close to 99.9 per cent of all the mass in the solar system. It is at a temperature of millions of degrees Celsius and so everything, including metals like iron and uranium, turns into plasma — electrically charged, hot gas.

Apart from its massive gravitational field, the sun has a massive magnetic field.  Plasma moves around continuously, which means that the electromagnetic fields also constantly shift.

When the sun is totally eclipsed, you can see a wide shining ring around the black disc obscured by the moon. That is the corona — the solar atmosphere, which consists of flares of plasma moving around randomly.

The corona “sheds” continuously with charged particles being pushed out of the sun in a stream. This is referred to as the solar wind although this doesn’t really contain any breathable gas. It has been theorised that you could build a spacecraft with “sails” to catch these particles, which would then propel the spacecraft along. (Google “Sunjammer — solar sails design” if you want to know more.)

Every 11 years or so, the sun’s magnetic field flips completely — that is, the sun’s North Pole becomes its South Pole and vice-versa. The variations in magnetic fields can lead to the ejection of huge amounts of material — what’s known in the jargon as CMEs.

The last flip was late 2019 and activity is building up and expected to peak in mid-2025.

Larger CMEs can aggregate to billions of tonnes of material being spewed out in a few bursts. These CMEs are what cause the aurorae — the beautiful Northern and Southern light shows in the sky, visible from near the Poles.

They also have less desirable effects. They cause static that affects radio signals, and this can lead to disrupted communications for planes in flight. Satellites and mobile phones also work on radio waves, which can be disturbed by CMEs. They can also cause misbehaviour in old-style magnetic compasses.

A less visible but dangerous possibility is high radiation. Life on Earth is protected from harmful solar radiation by our magnetic field, and a thick atmosphere. The Earth’s magnetic field helps to trap a large proportion of the solar radiation high up, in a region called the Van Allen Belts. When big CMEs occur, there’s more radiation getting through the Belts.

Back in the 19th century or earlier, all this would have been barely noticed, except perhaps by scientists studying the sun. However, once humans started using radios, interference with communications became an issue. Given that the world is now crisscrossed with power grids and we depend on satellites for practically all our communications, locational and entertainment needs, CMEs are much more likely to disrupt daily lives. As satellite-based technologies become more sophisticated, their vulnerability to solar storms also increases.

Nasa classifies solar storms at five levels: from G1 to G5, with the G5 being strong enough to lead to power failure in electric grids, mobile networks and GPS.

So, engineers and scientists will be studying the recent episodes closely because more frequent and violent CMEs are expected through the next few years, with a peak in 2025.