Aurorae are nothing new. We’ve talked about them before, whether it was citizen scientists helping understand the STEVE phenomenon or aurorae on other planets like Jupiter and Saturn, we are all fascinated by their beauty. And yet, there are still unexplained phenomena when it comes to aurorae. Today, however, there is one fewer mystery. Allow me to introduce you to the space hurricane.
Let’s start with the basics. Aurorae occur when charged particles, electrons generally, interact with atoms high in the Earth’s atmosphere. The electrons change the state of the atoms, increasing their energy, but that isn’t a stable state. The atoms then lose that energy and return to their original stable state, and the energy is released as photons of light, creating the gorgeous colors in the sky.
Where do the charged particles come from? The Sun. In particular, they are carried on the solar wind, and when the Sun is in its more active phases, we frequently get aurora alerts. Anytime there is a coronal mass ejection, we can definitely expect aurorae in the highest latitudes around the polar regions. If an ejection is particularly large, the aurora can extend into the mid-latitudes. I know my family in Minnesota has been able to see them.
However, aurorae don’t just happen when the Sun is energetic. There have been numerous instances of spectacular aurorae occurring when the Sun is quiet and there is little solar wind. So a research team combed through thousands of aurora images to understand why these events occurred. They found several dozen instances, and one event, in particular, lasted for eight hours, giving the team a lot of data to work with. And what they found was that these aurorae were spiral-shaped and circular like a hurricane.
That eight-hour hurricane occurred on August 20, 2014, and it was made of spiral arms of plasma that were over 965 kilometers long, spinning around a calm center. Instead of water falling, these atmospheric storms rained electrons over the magnetic North Pole.
Unlike their more terrestrial counterparts, these space hurricanes aren’t a large risk to humans on the surface, but they are important to understand because all that energy can cause fluctuations in radio waves that pass through the ionosphere. That could affect our satellite communication and maybe even navigation. Plus these storms might heat up the upper atmosphere, which would expand as a result, changing in density, and all of that becomes an issue for the satellites and space debris that orbit at that elevation. Change the drag on a craft, and you change its velocity. That makes orbital predictions more difficult.
As coauthor Larry Lyons notes: If you want to know where the space station is going to be a few hours from now, you have to know what kind of an atmosphere it’s going through.
There are still a lot of open questions about these newly discovered space hurricanes, and lead author Qing-He Zhang lays them out: What controls the rotation of space hurricanes? Are these space storms seasonal like their tropical counterparts, perhaps limited to the summer when the Earth’s magnetic dipole is tilted just the right way? And can space hurricanes be forecasted like weather events on Earth?
Pamela and I are both excited to see where this new avenue of research goes. Aurorae are just cool.
“A space hurricane over the Earth’s polar ionosphere,” Qing-He Zhang et al., 2021 February 22, Nature Communications