Diving deep into the magnificent auroras

Image from: National Geographic

Introduction to auroras

All of us have heard of Auroras and perhaps even seen them. They’re one of the most spectacular natural phenomena! In simple terms, they are shimmery lights that display in the sky that are only visible at night.

What causes auroras?

Now, the important talk about how they occur. Auroras are produced when the Earth’s magnetosphere swings back and forth or oscillates while interacting with the Sun’s solar wind. The Sun is full of electrically charged particles, called ions, and the solar wind is when these particles are ejected from its upper atmosphere named the corona. Earth’s magnetic fields protect our planet from such space weather since they can cause disruptions in our atmosphere and even prevent life.

Vocabubbleary: The magnetosphere is an area surrounding a planet controlled by its magnetic field. Our Earth has a teardrop or comet shaped magnetosphere which is the strongest one in our solar system!

Image from: National Air and Science Museum

When the magnetosphere blocks most of the solar wind, the ions are forced around the planet and farther into the solar system. However, some of the ions get trapped in the two belts in the magnetopause called the Van Allen Belts. When magnetic reconnection occurs, the particles rain down into our atmosphere toward the poles. As this happens, the ions in the solar wind collide with atoms in the Earth’s upper atmosphere. These areas, part of our atmosphere, are called the ionosphere which are centered around Earth’s geomagnetic poles. When these atoms get excited by this reaction, they emit light as they return to their original state. This forms the auroras that glow within bands called the Auroral Ovals which are twin halos encircling the two poles of Earth.

Image from: NASA Space Place

Vocabubbleary: Magnetic reconnection is the process of magnetic field lines opposite from each other break apart and rejoin in a plasma. The magnetic field energy is converted into plasma thermal and kinetic energy. In the case of auroras, the plasma formed from the reconnection is what accelerates the ions into the Earth's atmosphere.

Billions of these individual collisions continue at lower and lower altitudes until all the energy is used up, lighting up the magnetic field lines. Adding onto that, auroras generally occur around 97-1000 kilometers (60-620 miles) above Earth’s surface.

You may also be wondering what causes the different colors in auroras. There are a few factors affecting this such as the altitude or the type of atoms involved. Since our atmosphere is made of different particles, these atoms glow in lights of different colors. For example, oxygen emits a greenish-yellow color, nitrogen produces red light while hydrogen and helium emit blue or purple auroras. However, our eyes are unable to see this as it falls under ultraviolet light on the electromagnetic spectrum.

Lastly, if you’re concerned if auroras are dangerous, fret not since they do not threaten our existence in any way! However, active auroras may occasionally interfere with radio and radar signals.

What are the types of auroras?

There are two types of auroras; aurora borealis (also known as the Northern Lights) and aurora australis (Southern Lights). Both of these are breathtaking and colorful displays of light but the only difference is where they occur. Aurora borealis happens in the northern hemisphere while aurora australis happens in the southern hemisphere.

Vocabubbleary: Hemispheres are the two equal halves of Earth. We have four hemispheres; northern, southern, western and eastern. The equator (0° latitude) divides the planet into the northern and southern hemispheres while the prime meridian (0° longitude) divides it into western and eastern. The climates of the northern and southern hemispheres are different since they receive different amounts of the sun's light due to the tilt of the Earth.

Image from: Time and Date

Another difference in auroras is their shape. Although this has not been thoroughly explored by scientists, the shape depends on where the ions collide in the magnetosphere and what resulted in them leaking into our atmosphere. Even auroras happening on the same night can look incredibly different!

Where and when to see auroras

Since the halo created by the collisions occurs near the poles, auroras can only usually be seen in polar regions near the Arctic and Antarctic circles. The best places where you can see the northern lights, or aurora borealis, include Iceland, Fairbanks in Alaska and Yellowknife in Canada. Northern lights are usually visible during the months of September through mid-May since there is usually more solar activity in that period.

You may have realized that northern lights are more talked about than southern lights which is because there are not as many places to see aurora australis from the Southern Hemisphere. Still, there are some locations such as Mount Wellington in Tasmania and Queenstown in New Zealand. As for aurora australis, they are more commonly seen from May to September, during winter and the spring equinox.

Vocabubbleary: An equinox is where the sun's rays shine at 90° to Earth's surface and passes through the Earth's equator. Only during an equinox, Earth's axis does not tilt toward or away from the sun. This makes both the northern and southern hemispheres experience approximately equal durations of daytime and nighttime.

Image from: National Geographic Education

☕ Hubble Tea of the post! ☕

Today, we'll be learning about Hubble's discovery of a Galactic Jellyfish! The galaxy in the image is called the galaxy JW100 which is over 800 million light years away. It looks like a disk leaving behind a trail of star-forming gas in a process known as ram pressure stripping. This happens when galaxies travel through a gas spread out in galaxy clusters that strips away dust and gas from the galaxy, forming the stream as shown here.

Image from: NASA

In this post we’ve learnt the scientific explanation behind the dancing lights of the aurora that provide magnificent views. I hope you can appreciate auroras more after reading and consider seeing them one day! They're definitely worth the time, cost and cold weather to watch them in your lifetime!

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