Electricity & Megnetism

Physics of the polar aurora

Polar auroras are natural phenomena that light up the night sky at the planet’s poles. The physics of magnetism explains how this phenomenon occurs.

Auroras occur because of the collision of particles coming from the Sun with the Earth’s atmosphere.
Polar auroras are phenomena characterized by an intense glow in the night sky of regions close to the Earth’s poles . This glow, usually green, is the result of the interaction of particles coming from the Sun with molecules of oxygen and nitrogen present in regions that correspond to the terrestrial ionosphere.

The phenomenon is called aurora borealis when it occurs in the northern hemisphere and aurora australis when it occurs in the southern hemisphere.

How do polar aurora occur?

It all starts in the sun! At all times, due to explosions of nuclear reactions , the solar corona, the outermost layer of the Sun, ejects elementary particles with very high energy. The particles are ejected in all directions around the star and make up the so-called solar wind .

Upon reaching Earth, the particles collide with the Earth’s magnetic field. Every electrically charged particle that moves in a region where there is a magnetic field is subject to a magnetic force . This force acts on the particles of the solar wind, driving them according to their electrical charges towards the northern or southern regions of the Earth.

solar wind illustration

Upon reaching the regions of the ionosphere, the particles collide with molecules of oxygen and nitrogen. The collisions provide energy to the molecules of these elements, thus, the constituent electrons of these molecules are positioned in more energetic layers. Upon returning to the source layer, the oxygen and nitrogen electrons release the light that illuminates the skies. A similar process occurs in the operation of a fluorescent lamp .


If the particles were not deflected by the Earth’s magnetic field, numerous technologies would be harmed. GPS devices, radio frequency communicators communicators , data transmission via the internet, among others, would be totally harmed by the presence of elementary particles coming from the Sun.

In 1859, abnormal activity on the Sun generated a solar storm that brought an exorbitant amount of particles to Earth. At this time, the polar auroras were intensified, and the telegraph service was totally compromised.

Auroras in other worlds

Polar auroras are not unique to Earth. Planets like Mars , Jupiter and Saturn produce magnetic fields strong enough for the aurora phenomenon to occur.

In 2014, the Mars Express spacecraft detected an aurora polar on the planet Mars. Polar auroras on Jupiter and Saturn were detected by images taken by the Hubble Space Telescope.

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