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EXPLAINED: What Happens When Millions Of Hydrogen Bombs Erupt On Sun's Surface

The Sun's surface is marked by constant activity of the solar gases

The Sun's surface is marked by constant activity of the solar gases

A solar flare was witnessed last week that is said to have caused minor radio blackout in some parts of Earth. Here's what you need to know about the phenomenon

On July 3, the Sun sent out an intense blast of radiation towards the Earth that was its biggest since 2017. Known as solar flares, these bursts of energy can threaten satellites and communication grids although humans on Earth are protected from its effects by the atmosphere. So, what are solar flares and solar cycles and why scientists are watching out for these events.

What Is A Solar Flare?

To understand solar flares we have to first find out what sunspots are that dot the surface of the sun. According to US space agency Nasa, sunspots are the darker patches on the surface of the gas bubble that is the sun. If they appear dark it is because they are also cooler than the surrounding areas and are linked to magnetic fields on the Sun. Nasa says that “these magnetic fields are so strong that they keep some of the heat within the Sun from reaching the surface, which would explain why these spots are cooler.

The temperature of a sunspot can be in the region of about 3,500 degrees Celsius, not cool you will say. But compare that with the 5,600 degrees Celsius that is the normal temperature for the surface of the Sun.


Magnetic fields or lines can be unstable and end up tangling and crossing each other. When that happens, it can unleash a sudden blast of energy, which scientists on Earth have named as a solar flare. These solar flares can send out massive amounts of radiation into space and, if very intense, these can interfere with radio communications on Earth.

That is exactly what happened on July 3. A sunspot called AR2838 produced a flare that was said to have caused a minor radio blackout on Earth.

How Intense Was The Solar Flare Of July 3?

When the Sun spins out a solar flare, it releases a range of electromagnetic radiation from radio waves to x-rays and gamma rays. Nasa says that “the amount of energy released is the equivalent of millions of 100-megaton hydrogen bombs exploding at the same time". The soace agency adds that while large flares can emit energy at a scale that “ten million times greater than the energy released from a volcanic explosion… it is less than one-tenth of the total energy emitted by the Sun every second".

Classified according to their strength, the biggest flares are notified by the letter X while the smaller ones are designated by the letters A B, C and M, in that order. Each letter category denotes a 10-fold increase over the preceding class. Thus, X is 10 times an M category flare, but 100 times a C class solar flare. Nasa adds that “within each letter class there is a finer scale from 1 to 9".

The July 3 flare was measured as an X1 flare, measuring at X1.59, which means it was one of the smaller examples of the bigger, that is, X category flares. The last big flare, in 2017, was recorded as an X8.2-class flare. Nasa says that the “biggest X-class flares are by far the largest explosions in the solar system".

The mother of all solar flares recorded by scientists on Earth was one that appeared in 2003 and was measured at X28 before the sensors were overwhelmed by its brightness. That flare had come during the peak of a solar cycle and experts say that the Earth should gear up for more intense solar flares in the next few years after the sun began a new cycle in 2019.

What Is A Solar Cycle?

The solar cycle is linked to the Sun’s composition as a ball of hot gas. The gases that make up the Sun are in a constant state of flux and linked to their movement are the magnetic fields whose tangling and overlapping gives rise to solar flares. This magnetic field, interestingly, is what lies at the heart of solar cycles.

About every 11 years, Nasa says, “the Sun’s magnetic field completely flips", meaning its north and south poles are interchanged. This solar cycle, “affects activity on the surface of the Sun, such as sunspots. As the magnetic fields change, so does the amount of activity on the Sun’s surface".

As a new cycle begins, the Sun is said to be at a solar minimum. This is a period when the Sun has the fewest sunspots. Then comes the period of solar maximum, when the solar cycle is at its middle and the Sun has the highest number of spots. It is also the time when the biggest solar flares can be expected, experts say. Now, given it started in 2019, it is around the middle of this decade that the biggest solar flares of the present cycle may occur.

However, such trends are not certain and Nasa says that while “some cycles have maximums with lots of sunspots and activity, other cycles can have very few sunspots and little activity". Which is why scientists spend considerable effort to study solar activity and predict the occurrence of solar flares, given the impact they can have.

What Damage Can Solar Flares Cause?

According to Nasa, “forecasting of the solar cycle can help scientists protect our radio communications on Earth, and help keep Nasa satellites and astronauts safe". That is because, energy from solar flares can mess up electronics on board satellites and spacecraft while the radiation “can be dangerous" for space travellers who may be doing a spacewalk at the precise moment when a solar flare hits.

Scientists also point to a phenomenon called ‘coronal mass ejection’, or CME, which can accompany solar flares. CMEs are defined as “huge bubbles of radiation and particles from the Sun" that are launced into space “at very high speed when the Sun’s magnetic field lines suddenly reorganise".

You can see CMEs at work in the brilliant displays of light called auroras at the poles. However, if they are strong, CMEs can end up affecting electricity grids, leading to power outages.

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first published:July 06, 2021, 14:14 IST