As our star nears its peak of activity, two enormous dark holes have been discovered on our sun. As a result of these coronal holes, solar winds can travel at 1.8 million mph toward our planet, causing stunning auroras and disrupting satellites.
When such holes occur at the same time as another big solar event, they can cause a “perfect storm” that disrupts power grids and causes radio blackouts.
The following is an explanation of what coronal holes are, how they form, and what they could do to the Earth:
Magnetic fields on the sun create coronal holes
Liquid, charged particles boil up from the sun’s center, gurgle around on the surface, and sink back to the ground.
Like a wire coil charged with a magnetic field, the plasma on the surface of the sun creates magnetic fields as it travels around.
Magnetic fields live in harmony when the sun is fairly quiet, but when our star reaches a peak of activity, like it is now, they clash, merge, and split.
Occasionally, these fields point straight up into space, creating a coronal hole.
Solar winds are not created by coronal holes, they are just released by them
A magnetic field around the sun usually prevents plasma from escaping.
Mathew Owens, professor of space physics at the University of Reading, said charged particles must follow the magnetic field.
“When you see all these loops on one of these nice images, you’re seeing charged particles.”
Open field lines, on the other hand, point straight out into space, allowing plasma from the sun to shoot outwards. This propels enormous amounts of plasma into space.
Up to 1.8 million miles per hour are traveled by the coronal winds
Up to 1.8 million miles per hour, solar winds can hurtle through space when coronal holes release them.
Scientists are still debating why these winds travel faster than other solar winds.
Winds are said to be propelled forward by the movement of the field lines themselves.
In this bubbling surface plasma of the sun, when you stick open magnetic field lines, they start shaking. According to Daniel Verscharen, an associate professor of space and climate physics at University College London, they move upward like waves, giving the solar wind extra energy.
On their own, solar winds aren’t too dangerous, but they can cause trouble.
“The biggest overall shows and the most hazardous space weather are all caused by coronal mass ejections (CMEs),” said Owens.” But fast winds can have effects too. It’s just not as spectacular.”
Known as the Van Allen radiation belt, the Earth is surrounded by a layer of fast-traveling magnetically-charged particles.
This belt is disrupted by particles coming from the sun. Coronal winds from the sun aren’t very strong compared to clouds ejected by CMEs.
If the Earth is exposed to a long-lasting stream of fast winds from a coronal hole, it can actually put a lot of energy into the Earth’s system,” Versharen said.
Although it won’t be as spectacular as when a coronal mass ejection lands on Earth, it can still enhance aurora displays.
Satellites in orbit can be damaged by those particles.
Verscharen said, “If you’re lucky, they’ve just changed a few things in the electronics, flipped a bit over to another value. So you get some weird disturbances that you can then correct. But in the worst case, they can destroy the satellite.”.
Solar winds combined with coronal mass ejections pose the greatest danger
CMEs and coronal holes are of greatest concern to scientists.
If a CME is aligned with Earth, that cloud of plasma can strike our planet much more violently than solar winds if closed magnetic loops snap in half.
Versharen said, “That’s the stuff that scientists are nervous about.”.
As those CMEs approach Earth, they can become much more powerful if they are near a coronal hole.
According to Owens, there is a low likelihood of CMEs occurring within coronal holes. However, if a fast wind comes behind, it can compress and accelerate those CMEs.
Solar physicists call this “a perfect storm,” according to Alex Young, associate director for science at NASA Goddard’s Heliophysics Science Division.
As far down as New Mexico, auroras were seen during the week of March 24.
There were coronal mass ejections that burst right next to the coronal hole, turning what scientists had thought would be a category G2 storm into a category G4 storm.
The winds could have created a G5 storm, which can take down power grids.
Suns don’t have holes in their coronals
It looks like someone has gouged a divot in our star when the sun has a coronal hole.
Coronal holes appear on UV imaging, which shows very hot, magnetically active areas on the sun.
The region inside the hole is cooler and less active because it is losing material.
The open field allows material to escape into space, so there is less material in the field.
Coronal holes rarely line up with the Earth
Because they tend to stay near the poles of the sun during quiet times, coronal holes don’t usually line up with the Earth.
According to Owens, these coronal holes usually occur at the north and south poles of the sun.
When that happens, the winds are being ejected into space and won’t line up with the Earth.
As a result of the sun’s current solar maximum, which occurs about every 11 years when solar activity is at its peak, these open magnetic field lines are more likely to appear around the equator, where they can be pointing straight at the Earth during this period.
We do start seeing more of these coronal holes reaching down to the equator as solar activity ramps up towards the solar maximum. This makes it easier for the fast wind to hit Earth,” Owens explained.
There is a difference between a coronal hole and a sunspot
To the untrained eye, coronal holes and sunspots may look similar.
Sunspots occur on the surface of the sun and can be seen with the naked eye, while Coronal Holes occur in the atmosphere of the sun and are only visible with UV or X-ray lights.
Coronal holes occur when magnetic lines point straight outward from the sun, while sunspots occur at the ends of curved magnetic lines that curve up and back down as if they were a rainbow.
Coronal mass ejections can be created by sunspots, but not by coronal holes.
Next month, we might see the same coronal holes as this month
In spite of the fact that the holes spin around the sun and are out of sight, they may still be spewing solar winds away from us.
As they rotate back into view in about a month – enough time for the sun to rotate – we might be able to see them again.
However, they may disappear at any time.
“These holes at the equator tend not to last as long as the ones at the poles, which will remain there for years at a time,” Owens said.
When they’re at the equator, everything on the sun is just changing rapidly,” he said.
It will be possible to see coronal holes a few days earlier thanks to a mission
We are about forty years behind in space weather predictions, according to Verscharen.
An European Space Agency mission called Vigil, planned to launch mid-2020s, aims to solve this problem by looking at the back of the sun.
Satellites will still be able to communicate with Earth, but will be able to see the sun from a different angle.
“So when you look at the sun from there, you can see the surface four and a half days before,” said Verscharen.
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