Rick Robinson

Sep 19th 2022

An Explosion on the Sun


On Easter weekend, as people were heading out to soak up some rays as spring came into bloom, the sun blew up in a spectacular eruption. According to Interesting Engineering, the blast rated X1.1 on the NASA classification scale of solar storms, placing it in NASA’s most powerful class of solar flares.

A few days later, another explosion on the sun was even more powerful, rating at X2.2 on the NASA scale. Explosions on the sun are on the rise.

When the Sun Explodes

As we head into summer, the good news for beachgoers — not to mention for life on Earth — is that these sun bursts pose no direct threat to human or other life. An explosion on the sun won’t even cause you to get a worse sunburn.

What it can do is disrupt radio communications and knock out orbiting satellites. A similar eruption earlier this year, notes Interesting Engineering, fried more than 40 satellites just after being launched into orbit.

As Live Science explains, the general term for sun bursts or explosive eruptions on the sun is “solar flares,” and they’re closely linked to sunspots. The literally underlying story here is that enormous amounts of energy are continually produced by nuclear fusion in the sun’s core. This energy gradually works its way outward until it reaches the visible solar surface, where the energy breaks free and streams off into space as sunlight.

This energy flow is turbulent — think of a bubbling, whistling tea kettle, scaled up about a trillion times. Turbulent and extremely hot gas generates powerful magnetic fields, resulting in even more turbulence.

All of this activity produces (relatively!) cooler areas on the solar surface, darker than their intensely bright surface around them, that are visible from Earth — with suitable precautions! — as sunspots. These cooler areas, however, are balanced by hotter areas nearby, where magnetic fields twist, snap and reform. And each time they do so, the result is an explosive eruption on the sun: a solar flare of X-rays and other radiation, and a prominence, or stream of electrically charged gas hurled into space.

Solar Storms and the Solar Cycle

Dramatic time-lapse footage of solar prominences shows that most of this glowing material falls back onto the sun. But some of it is blasted outward with enough power to overcome even the sun’s mighty gravity field, hurling outward into space as a coronal mass ejection, or CME.

If it happens to be blown outward in the right direction, the result in a day or so will be a stream of fast-moving charged particles passing Earth. Some, trapped by Earth’s magnetic field, will be deflected into the upper atmosphere, particularly at polar latitudes, triggering beautiful auroral displays in the night sky.

Sunspots and the eruptions associated with them tend to rise and fall in numbers and intensity over a cycle of about 11 years, per Interesting Engineering, a fact that has been known since the 18th century. The sun is currently in the upswing phase of the 25th cycle since astronomers began keeping count: A NASA blog, updated regularly, tracks and reports on each eruption as it’s detected.

Measuring Solar Storms

Each eruption’s strength is measured and reported on a scale comparable to the scales used for measuring earthly storms and earthquakes. A decade ago, during the last solar cycle, NASA produced a more detailed account of this measuring scale. The least energetic solar flares are assigned to class A, with successively more powerful flares rating as class B, C, M and X, the most powerful category.

As with the Richter scale for earthquakes, each class is 10 times more energetic than the class below it, as measured by the intensity of X-rays an explosion on the sun produces. Thus, classes A, B, C and M are all divided into 10 subclasses. Because class X is the most powerful, it’s the only class with more than 10 subclasses.

Classes A through C have no disruptive effects near Earth, while class M flares can cause minor disruptions of radio signals. Class X flares, the most powerful, can lead to more widespread disruptions.

The recent twin blasts were both powerful enough to reach class X (X1.1 and X2.2), while the most powerful explosion on the sun yet recorded with modern technology, in 2003, overloaded the sensors when it hit X28.

It kind of makes you want to go to the beach, put on your shades, slather on some sunscreen and enjoy a nice, toasty explosion on the sun.

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