It seems we haven’t seen the last of the biggest sunspot in 24 years. In fact, not only is it rotating back to face Earth, but it seems to have gotten even larger. Last month, this sunspot showed up in the AR12192 solar active region and it could easily be seen with the naked eye – wearing appropriate protective glasses of course. It honored us with a series of impressive flares before disappearing on the far side of the sun.
However, it seems it wasn’t done making an impression because AR12192 rotated back to our neck of the woods on November 12th, allowing us to see the sunspot again, which has obviously increased in size. In fact, it’s grown so big that one of the edges was visible one day before it fully rotated towards us again.
Charles Lindsey from North West Research Associates (NRWA) in Boulder, Colorado, has been keeping a close eye on this solar active region and has monitored its progress ever since it disappeared around the western side of the sun a few weeks ago. According to his calculations, the sunspot has definitely grown considerably.
It has been 27 days since we have been able to see AR12192 head-on because that’s about how long it takes the sun to rotate as we see it from Earth. However, Dr. Lindsey and Doug Braun, his colleague, developed acoustic holography – a helioseismology technique – which allows them to “visualize” areas with significant activity on the other side of the sun using computational regression of the oscillations or waves seen on the side facing us back to the source, which is on far side.
Why Is It So Active?
An active area on the sun is caused by gigantic clusters in the magnetic field that rise up from the sun’s interior to the surface, while a sunspot is the area where the field is strongest, reaching approximately 3,000 Gauss. Compare that to the Earth’s magnetic field, which is approximately 0.5 Gauss.
The magnetic field is the main inhibitor of the boiling convection we can see on the surface of the sun. Convection is the process whereby most of the energy generated by the sun’s nuclear furnace, which resides in its core, is brought up to the external 29 percent of the sun. And that’s why a sunspot looks dark because the magnetic field is stopping this energy from reaching the surface.
Currently, the sun has almost reached the peak of Solar Cycle 24, which refers to the 24th cycle of the sun’s activity since we started recording it in detail in 1755. This is important because it can give us valuable information, such as the fact that sunspots tend to increase and decrease in numbers every 11 cycles. Also, the current cycle is quite weak by comparison to other cycles seen over the last century, but despite this weakness, it still seems quite capable of giving us a few impressive ones.
However, active areas don’t just produce sunspots as they also create flares, which are the most high-energy events in our solar system. Flares are the result of the magnetic field twisting and stretching to such a degree that it breaks, similar to the way an elastic breaks if you stretch it too far. It immediately reconnects to other lines in the field but it causes the release of massive energy bursts that can last several minutes. The biggest X-class flares can release as much as 6 x 1025 Joules of energy, which is approximately 100,000 times the amount of energy we use on Earth in a year.
Active areas are also often the source of coronal mass ejections or CMEs, which are huge gas bubbles that can weight up to 100 billion kg. These bubbles burst into space at high speeds of as much as 1,000 km per second and they carry massive amounts of magnetic flux and charged particles.
There seems to be an association between coronal mass ejections and flares, as they often accompany one another. However, this isn’t always the case and a flare that doesn’t come with a CME is referred to as being ordinary.
The first time it passed us, the large AR12192 was about the same size as Jupiter and created a few ordinary large X-class flares and a number of flares that were smaller in size. However, no large coronal mass ejections were witnessed.
However, Hugh Hudson from Berkley, California’s Space Sciences Laboratory points out that the older an active area is, the more coronal mass ejections it tends to create, so he thinks there’s a good chance of a large CME showing up on this pass.
How Does It Affect Earth?
Coronal mass ejections can have a significant effect on the magnetosphere of Earth, resulting in power outages, communications interruptions, and amazingly beautiful aurorae. They can also damage satellites that are orbiting the planet.
For example, the Carrington flare that erupted in 1859 created an aurorae that could be seen in Queensland, Australia. It also caused damage to telegraph stations all over the plant. Unfortunately, our modern technology is a lot more susceptible to the effects of flares and CMEs.
So, when AR12192 is facing us again, if it sends any big coronal mass ejections in our general direction we need to be prepared. This can include rerouting aircraft flying polar routes, disengaging long-distance electrical grids and making sure satellites are placed in safe mode.