Northern Lights, definition and study. A-Z index of Cognitio.

It is an optical phenomenon of the Earth’s atmosphere, characterized mainly by luminous bands of a wide range of shapes and colors rapidly changing in time and space, typically red-green-blue, called aurora arches.

Atmosphere, definition and study. A-Z index of Cognitio.

Atmosphere

The phenomenon is caused by the interaction of charged particles of solar origin with the terrestrial ionosphere: these particles excite the atoms of the atmosphere which, after de-energizing, emit light of various wavelengths. The auroras visible to the naked eye are produced by electrons, while those of protons can be observed only with the help of particular instruments, both from the ground and from the space.

Cosmic space, definition and study. A-Z index of Cognitio.

Cosmic space

Often the polar aurora is also visible in areas less close to the poles, such as Scotland, or many areas of the Scandinavian peninsula. The auroras are more intense and frequent during periods of intense solar activity. The origin of the aurora is 149 million km from the Earth, that is on the Sun.

Earth hollow theory, definition and study. A-Z index of Cognitio.

Earth hollow theory

The appearance of a large group of sunspots is the first sign of an expulsive activity of intense coronal mass. The energetic particles emitted by the Sun travel in space forming the solar wind.

Sun, definition and study. A-Z index of Cognitio.

Sun

This moves through the interplanetary space (and therefore towards the Earth, which can reach in 50 hours) with speeds typically between 400 and 800 km / s. The solar wind, by interacting with the earth’s magnetic field, also known as the magnetosphere, distorts it, creating a sort of magnetic “bubble”, similar to a comet. The particular colors of an aurora depend on which gases are present in the atmosphere, their electrical state and the energy of the particles that strike them. Atomic oxygen is responsible for green color and molecular oxygen for red. Nitrogen causes blue color. Sometimes, during the appearance of an aurora, sounds that resemble hisses can be heard. It is about electronics sounds, a phenomenon that can manifest itself, albeit more rarely, even during the appearance of bolides. The origin of these sounds is not yet clear: it is believed that they are due to perturbations of the local terrestrial magnetic field, caused by an increased ionization of the overlying atmosphere. 

Planet Earth is not the only one from which this phenomenon can be admired. The Voyager 1 and 2 probes have also photographed it at the poles of Jupiter, Saturn, Uranus and Neptune; after them, Hubble also started a long series of sightings.

Jupiter, definition and study. A-Z index of Cognitio.

Jupiter

Extraterrestrial auroras are often very spectacular due to the intensity of the magnetic fields of the respective planets. That of Uranus has unique characteristics, because the planet rotates tilted to the side, but its magnetic field is almost vertical.

Uranus, definition and study. A-Z Index of Cognitio.

Uranus

In the case of Uranus, the polar aurora resembles more dots of light than rings.

Northern Lights, definition and study. A-Z index of Cognitio.

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Northern Lights, definition and study. A-Z index of Cognitio.

Northern Lights