The Sun Hurls its Most Powerful Flare in a Decades

The Sun has been vying for attention these last couple of weeks. First with the appearance of a fabulous complex sunspot region and then with a plethora of solar flares. On the 14th May, yet another was released, this time an X8.7 class flare from the same complex sunspot regions. It was significantly more powerful than the flare that set off the aurora displays which enchanted much of the planet but alas it was not pointing toward the Earth ( sad emoji face.) Even though it was not directed at us, it could still disrupt communications and electronics but is a reminder that the Sun, whilst is on its way to solar maximum still has lots to give.

The Sun is a great big ball of plasma (electrically charged gas) and like Earth, it has a magnetic field. One of the properties of plasma is that any magnetic field that runs through it, will get dragged along if it moves. Equally, if the magnetic field line moves then it takes the plasma with it. 

Like all astronomical objects, the Sun rotates on its axis but the equatorial region rotates faster than the polar regions. The result of this, over time, is that the magnetic field lines get wound up tighter and tighter. They can only take so much stress and straining and on occasions will snap, sometimes burst through the visible surface and lead to the formation of sun spots. 

Sunspots captured by NASAs Solar Dynamic Observatory

The appearance of sunspots changes over an 11 year period known as the solar cycle. At the start of the cycle, the magnetic field lines are reasonably straight so we experience no disturbances and no sunspots. As the cycle progresses and the field lines start to get stressed, the sunspots first start to appear around the polar regions and then slowly migrate toward the equator as maximum activity is reached. 

Heading toward maximum we can also see quite complex regions with multiple sunspots. When these appear the field lines can snap and release energy in a process known as magnetic reconnection and it is this that can generate events like the massive flare seen on the 14th May. 

The flare on the 14th was classed as an X9.7 flare. This classification system tells us just how powerful a flare is. The smallest flares are classed as B-class, the next are classed as C, then M and finally the largest most powerful flares are X-class. A C-class flare is 10 times more powerful than a B-class and an M-class is more powerful than a C-class. An M-class flare can cause communication troubles on Earth and some can put the health of astronauts at risk. 

X9.3 Flare blasts off the Sun. Image credit: NASA/GSFC/SDO

The numbers that follow are then a sub category refining the power level with B, C and M-class flares capable of being 1 – 9 since a B10 flare is equivalent to a C-class. When it comes to the X-class flares there are on occasions flares that are more powerful than an X-9. The most powerful flare on record was in 2003 when an X45 flare was recorded. Flares like this can harm satellites, astronauts in orbit and even passengers on board an aircraft would get a dose of radiation if flying close to the poles! 

Source : A Week of Rapid Fire Solar Flares

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