• The Sun emitted three strong solar flares, two on May 5 and one on May 6.

• NASA’s Solar Dynamics Observatory, which watches the Sun constantly, captured the image of the event.

• The first flare is classified as an X1.3 flare. The second flare is classified as an X1.2 flare. The third flare is classified as an X4.5 flare. 

• X-class denotes the most intense flares, while the number provides more information about its strength.

What is solar flare?

• Solar flare is a sudden brightening observed over the Sun’s surface, which is interpreted as a large energy release. 

• Flares can impact radio communications, electric power grids, navigation signals, and pose risks to spacecraft and astronauts.

• Flares are our solar system’s most powerful explosive events — the most powerful flares have the energy equivalent of a billion hydrogen bombs, enough energy to power the whole world for 20,000 years. 

• Flares are mainly followed by mass ejections from the solar atmosphere called coronal mass ejections (CMEs). The flare ejects clouds of electrons, ions, and atoms through the corona of the Sun into space. 

• Solar flares can last from minutes to hours. Sometimes the same active region on the Sun can give rise to several flares in succession, erupting over the course of days or even weeks.

What causes solar flares?

• Solar flares erupt from active regions on the Sun – places where the Sun’s magnetic field is especially strong and turbulent. 

• Active regions are formed by the motion of the Sun’s interior, which contorts its own magnetic fields. Eventually, these magnetic fields build up tension and explosively realign, like the sudden release of a twisted rubber band, in a process known as magnetic reconnection. 

• This rapid energy transfer creates solar flares as well as other kinds of solar eruptions like coronal mass ejections and solar energetic particle events.

Categories of solar flares

• Scientists classify solar flares according to their peak brightness in X-ray wavelengths.

• Solar flares are classified into different classes based on their strength, or energy output, and the effect a flare will have on Earth depends on what class it is.

There are five categories:

i) X-class flares are big. They are major events that can trigger radio blackouts around the whole world and long-lasting radiation storms in the upper atmosphere.

ii) M-class flares are medium-sized. They generally cause brief radio blackouts that affect Earth’s polar regions. Minor radiation storms sometimes follow an M-class flare.

iii) C-class flares are small with few noticeable consequences here on Earth. At its peak, a C-class flare is ten times less powerful than an M-class flare. 

iv) B-class flares are ten times smaller or weaker than C-class flares.

v) A-class flares are at least ten times less intense than B-class flares, with no noticeable consequences on Earth.

• To indicate the strength of a flare, the class letter is often followed by a number. The higher the number, the stronger the flare.

• Although X is the biggest category, there are flares more than 10 times the power of an X1, so X-class flares can go higher than 9. 

• The most powerful flare measured with modern methods was in 2003, during the last solar maximum, and it was so powerful that it overloaded the sensors measuring it. The sensors cut out at X28.

• If directed at Earth, solar flares and associated coronal mass ejections (CMEs) can create long lasting radiation storms that can harm satellites, communications systems, and even ground-based technologies and power grids.

What is the difference between a solar flare and a coronal mass ejection?

• Solar flares and coronal mass ejections (CMEs) both involve gigantic explosions of energy, but are otherwise quite different. 

• Solar flares are bright flashes of light, whereas CMEs are giant clouds of plasma and magnetic field. 

• The two phenomena do sometimes occur at the same time – indeed the strongest flares are almost always correlated with coronal mass ejections – but they emit different things, they look and travel differently, and they have different effects near planets.

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