Aurora Borealis - Wilderness North

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Aurora Borealis

Let’s Get Technical

The Northern Lights (or aurora borealis) are the result of the sun’s charged particles interacting with the earth’s atmosphere. The sun is continually releasing these particles in bursts (or solar flares), and episodes grow stronger for 11 years until reaching their peak.

  1. Be in the Right Place, at the Right Time
  • Travel as far north as possible.
  • Seek a place with little to no light pollution (a cottage resort or campground in our area).
  • Go in the fall or winter months, nights are clearer and provide longer periods of darkness. September and October are described as peak months.
  • On a clear night, observe the sky between 11 pm and 3 am local time.
  1. Observe Space Weather

Space weather? Huh? If you’re serious about viewing the lights, SpaceWeather.comis worth a look. X-ray solar flares (which cause the aurora) are classified and listed under Current Conditions.B class flares are basically non-existent, C class flares are small, M class flares are medium sized, and X class flares are the largest and cause the greatest amount of activity on earth. The larger the flare, the better your chances are for seeing the northern lights (in the right conditions, of course).

SpaceWeather.comprovides a 24-hour forecast, so it would be useful tool if you’re already at the cottage, or embarking on a spur-of-the moment trip north.

The colour of the aurora depends on what gas is excited or ionized and at what altitude this happens. At the highest altitudes oxygen atoms emit red light. At lower altitudes green light from oxygen atoms starts to dominate. When solar activity is very high, we may also see blue and purple light coming from the lowest part of an auroral display. Nitrogen molecules emit these colours.

So when you are lucky enough to see the spectacular display of the aurora, what you are really witnessing is the interplay between the Earth and the Sun’s magnetic fields and the energetic particles flowing through them. You are witness to the beauty of some very complex physical processes. The beauty of physics!

  1. Use Long Exposure

To the naked eye, northern lights are transient – here one moment, gone the next. But these moments can be captured using a Digital SLR camera. If you use long exposure, one photo can display up to 60 seconds of contrasting hues.

Although it’s possible to photograph with a point and shoot camera, it’s recommended that you use a DSLR with advanced settings. Check out photographer Roy Hooper’s article on Photographing Northern Lights with your Digital SLR for more information.

The story of the Northern Lights (or Aurora Borealis) starts deep inside the Sun. The core of the Sun is a nuclear furnace that converts hydrogen atoms into helium atoms through nuclear fusion. This is a process that releases a tremendous amount of energy. When you look at the Sun, essentially what you see is a huge hydrogen bomb that is contained by the force of gravity. It has been around for over 4 billion years, and about that much more time is left before the core runs out of hydrogen. All the energy that is generated in the core moves out through the Sun as electromagnetic radiation, or light.

You can imagine that if you were close to the surface of the Sun, the amount of energy hitting you would be tremendous. You could not survive there. Similarly the atoms in the solar atmosphere can’t get away unscathed either. Some of their electrons are stripped from them by the Sun’s energy, making them positively charged ions. This plasma (a gas of charged particles) is so hot it continuously expands outward through space creating a solar wind.

These solar wind particles carry a lot of energy, and eventually stream past the Earth’s own magnetic field, the magnetosphere. It is a huge windsock-shaped magnetic bubble, and acts as a partial shield against the solar wind. The magnetosphere also contains plasma, the origin of which is not well understood yet. The interaction of the solar wind and the magnetosphere drives huge electric currents in the magnetosphere. Because of these currents, the electrons and protons in the plasma come down in field lines.

An example of the electric current ‘field lines’.

The gas in the Earth’s upper atmosphere becomes excited and ionized as it absorbs the incoming energy. The atoms in our atmosphere re-emit this energy in the form of light – the aurora. Exactly the same way we make a neon sign glow by sending a current through it! The aurora mostly originates from a layer in the atmosphere about 80 km to 300 km above us. We see it in “sheets,” sometimes changing quite rapidly due to the shape and dynamics of the Earth’s magnetic field that guides the particles.

The flow of particles coming towards the Earth is usually roughly ring-shaped, centered around the magnetic poles of the Earth. In Ontario’s far north, for example Hee in Northwestern Ontario we usually have to wait for strong solar wind activity – a solar storm, which makes the ring of aurora around the north pole expand southward, to see the lights. Fortunately, a great deal of this activity has occurred in 2018, and continues into the fall.

To learn more about increasing your chances of viewing the northern lights, visit this recent article: Increase Your Odds: Viewing the Northern Lights. And, to view the northern lights from the comfort of home, you can check out the AuroraMAX cameraby the Canadian Space Agency.

 

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