The Physics Behind the Northern Lights

The Northern Lights

Auroras

The Northern Lights are a type of aurora borealis. Auroras near the South Pole are called aurora australis. This is caused by energetic - charged particles that emit red or green light. These auroras are typically only seen at higher latitudes or at the poles of the Earth. Every planet is surrounded by a magnetic field - some weaker than others. Auroras are caused by high energy particles typically blowing outward by the sun in solar wind that are caught in the Earth's magnetic field.

The picture above depicts the Earth's magnetic field lines - where it can be seen that all of the field lines end in the North or South Pole. This explains why the auroras are only seen in these two regions because all of the energized particles are attracted to the North or South Pole. Most of the particles that make up auroras are electrons, but protons can make auroras as well.

The Law of Conservation of Energy states that energy can never be created or destroyed. This is shown in auroras' emission of light. During the process of solar wind and transition into the electrical field, particles collide which results in excited/overcharged molecules. An excited molecule can only return to its ground state by sending off a photon; or making light.

NASA image by Polar Satellite, 2004

Relationship with Space

Auroras provide just one insight on how the physics of Earth and space stay balanced. The particles that are moved by the solar wind from the sun travel at 1/10 velocity of the speed of light. The Kinetic energy required to start this motion was contributed by the sun, still following the rule that energy is neither created or destroyed.

Norwegian physicist Kristin Kirkland attempted to recreate auroras in his lab in the early 1900s by mounting a sphere with a magnet in a vacuum chamber and directed it towards a beam of electrons. This actually produced light when the electrons traveled toward the magnet. This was the first attempt to explain the electric field that surrounds the Earth. It protects the Earth from solar system and without would tumble down to the Earth's surface. Energy is carried in a lamp through electric currents - and auroras do somewhat the same in traveling down the Earth's electric currents.

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