The aurora is the glow of the upper rarefied layers of the atmosphere caused by the interaction of atoms and molecules at altitudes of 90-1000 km with high-energy charged particles (electrons and protons) invading the earth's atmosphere from space. Collisions of particles with components of the upper atmosphere (oxygen and nitrogen) lead to the excitation of the latter, i.e. to a transition to a state of higher energy.
The return to the initial, equilibrium state occurs by the emission of light quanta of characteristic wavelengths, i.e. polar lights. It is observed mainly in high latitudes of both hemispheres in oval belts (auroral ovals), which surround the Earth's magnetic poles, at latitudes of 67-70 degrees. During times of high solar activity, the boundaries of the aurora expand to lower latitudes - 20-25 degrees to the south or north.
Auroras are most often seen in winter. Apparently, this opinion was formed from the fact that the auroras in Russia are very often called "northern lights" (after the name of the hemisphere where they are observed), and we associate the north with frost, snow and, accordingly, winter. In fact, auroras most often occur in the spring and fall, around the vernal and autumnal equinoxes, and repeat themselves in cycles lasting approximately 27 days and 11 years.
The aurora is born as a result of solar disturbances. This is confirmed by the cyclical nature of the auroras, which coincides in their highest peaks with the 27-day rotation of the Sun and 11-year fluctuations in solar activity, and their concentration in the zone of disturbances of the Earth's magnetic fields.
The aurora is just the light in the sky. At the same time, it is accompanied by a huge amount of energy, which is released in a relatively short period of time. The strength of the radiation can sometimes be equal to a 5-6 point earthquake. Pulsating aurora borealis can also be accompanied by faint whistling sounds or slight crackling.
The shapes of the auroras are different. Auroras are observed in various forms and shapes: spots, uniform arcs and stripes, pulsating arcs and surfaces, flashes, flashes, rays and radiant arcs, crowns. The glow of the aurora usually begins with a solid arc, the most common form of the aurora, and in the case of increasing brightness, it can take on other, more complex forms.
The color of the aurora depends on its intensity. The intensity of the aurora luminescence is determined according to the accepted international scale within I-IV points. Radiance with a low intensity of luminescence (from I to III points) does not seem to the human eye multi-colored, since the color intensity in them is below the threshold of our perception. Auroras with an intensity of IV and III (at the upper border) are perceived as colored - more often as yellow-green, less often - red and violet. Interestingly, most of the radiation is emitted by the main components of the high layers of the earth's atmosphere - atomic oxygen, which colors the auroras in yellowish tones, gives them a reddish radiance or brings a green line to the general spectrum, and molecular nitrogen, which is responsible for the main red and violet colors of one of the most beautiful celestial phenomena.
Stars can be seen through the aurora. Since the thickness of the aurora is only a few hundred kilometers.
The aurora is visible from space. And not just visible, but much better visible than from the surface of the Earth, since neither the sun, nor clouds, nor the distorting influence of the lower dense layers of the atmosphere interfere with observing the polar lights in space. According to the astronaut, from the ISS orbit, the auroras look like huge green constantly moving amoebas.
The aurora can last for days. Or maybe only a few tens of minutes.
The aurora can be observed not only on Earth. It is believed that the atmospheres of other planets (for example, Venus) also have the ability to generate auroras. The nature of auroras on Jupiter and Saturn, according to the latest scientific data, is similar to the nature of their terrestrial counterparts.
The aurora can be induced artificially. For example, with a nuclear explosion in the high atmosphere. Which was somehow done by the US Department of Defense. The American military managed to achieve shine from an arc of crimson color and smoothly passing from red through purple to green rays. Based on the color palette of artificial auroras, a theory was born that the reason for their occurrence lies in the excitation of oxygen and nitrogen contained in the atmosphere and their collision with charged particles released as a result of a nuclear explosion.
The aurora can be caused by rocket emissions. However, this phenomenon is usually called artificial glow, since the causes of its occurrence are close to those that cause the natural glow of the air.