An aurora is one of the most beautiful natural wonders of life on a planet with a global magnetic field, and experts in space weather are getting closer to understanding one of the mysteries of the phenomenon. You see, when a northern light lights up in the northern hemisphere, across the Arctic, the same pattern should eruption in the southern hemisphere skies over the Antarctic waters. But scientists noticed that the two did not match after comparing simultaneous images of north and south auroras in 2009.
Why should we expect them to be symmetrical in the first place?
How Auroras works
The Northern Lights is a visible reminder of the epic interplay between the sun's magnetic field and the global magnetic field of the earth, or the magnetosphere. The sun is constantly pumping huge amounts of energetic particles, such as protons, helium nuclei and traces of heavy ions. Together these particles are released in the interplanetary space and they wash the planets off as the solar wind.
Other solar phenomena, such as coronal mass ejections (or CMEs), explode and magnetize clouds of these particles into space at high speed. The solar wind, solar flares and CMEs, and the effects they have on our planet, are collectively known as & # 39; space weather & # 39 ;. All this space weather can have powerful effects on our planet – and our technology – as soon as it meets the magnetosphere of our planet.
Such an effect is a terrestrial magnetic storm. It can happen if the magnetic field of the sun interferes with the magnetosphere in a certain way, the magnetosphere being injected with solar particles that form aurora. Auroras develop when these particles follow the magnetic field of our planet to the poles and rain through the atmosphere. Depending on which atmospheric gases they hit, a beautiful colorful light screen will appear.
Now let's take a step back and imagine ourselves in those textbook diagrams of bar magnets, with at each end a north pole (N) and a south pole (S). The magnetic field lines that they create will identify symmetrical loops that connect the north and south poles. This is an oversimplification of the magnetic field of our planet, but physics is the same.
Let us then place the simplified magnetic field of our planet in a steady stream of particles from the sun. This current, or the solar wind, carries the magnetic field of the sun – known as the interplanetary magnetic field (or IMF) – which puts pressure on the magnetosphere of our planet and is flown back. The day side of our magnetosphere will be compressed, while the night side of the magnetosphere becomes elongated, such as a stretched water drop. If the solar wind was stable, not much would happen; the stream of particles would flow continuously over the Earth's magnetosphere. We know, however, that space weather is everything but steady.
While the sun is running, the solar wind is washing at different speeds across our local space, and eruptions such as torches and CMEs can cause very dramatic and dynamic changes in interplanetary space. If the magnetic conditions are good, the sun can throw a bubble of magnetized particles on Earth that will be injected into the layers of the magnetosphere (where you imagine that the layers of the magnetosphere-like layers of onion skin are not far removed from the actual structure). ). These particles are then swept back into the tail of the magnetosphere (appropriately called the "magnetotail") where they are stored until the magnetotail undergoes re-connection events, releases pressure and forces the stored solar particles to flow along the magnetic field lines to the earth's atmosphere. Magnetic reconnection is a phenomenon where magnetic fields are forced together, clicking as elastic and then reconnecting, releasing energy along with a huge wave of particles.
An asymmetrical reality
Because all things are the same and we remember our simple rod magnet scheme as described earlier, the field lines leading to the North and South Pole of the Earth should look the same and equal amounts of particles should rain in identical patterns across the Arctic and Antarctica. And this is where two new and additional studies, published in the Journal of Geophysical Research: Space Physics and the journal Annales Geophysicae, arrive.
In 2009, spacecraft experts compared the patterns of aurora that erupt during a terrestrial magnetic storm. What they saw was confusing; the patterns created were at different locations and had different forms than predicted. At the time, they assumed that this asymmetry was caused by the complexity of reconnection events in the magnetotail, as a result of which different quantities of charged particles were sent to the North and South Pole, which created the mismatch. However, these new studies indicate that the asymmetry is possibly caused by the orientation of IMF embedded in the flows of solar wind that first meets the magnetosphere of our planet – something that the researchers & # 39; asymmetric geospace & # 39; to mention.
Confused? The American Geophysical Union has produced an excellent video explaining this:
We can imagine the sun's magnetic field as a series of randomly oriented lines that wash over the earth as shallow waves would wash over a pebble on a beach. If they have a magnetic north-south orientation that corresponds to the north-south orientation of the magnetosphere, they will connect to the earth's magnetic field and reclaim, fuse with the magnetotail, along with the solar wind particles they contain. In this case, the magnetotail will appear symmetrical and all generated aurora's will also be symmetrical. Patterns linked!
But what if the magnetic field of the sun is oriented east and west in relation to the north-south field of the earth? According to these new studies, this can cause the magnetotail to be turned and asymmetrical. As you can probably guess, this will have an effect on the aurora that are produced, causing the solar particles to end up in an asymmetrical pattern and creating asymmetrical aurora. Patterns do not match!
In the course of time, as more and more energy is released through reconnection in the magnetotail, it will decay and these aurora will slowly return to their symmetrical form. This is not intuitive. Space weather experts once thought that the asymmetry was earlier causes by magnetic reconnection. In reality, it seems that reconnecting releases magnetic tension to bring the aurora to symmetry.