The aurora borealis is one of the many wonders of nature. It can also be observed in Russia. In the north of our country there is a strip where the auroras manifest themselves most often and brightly. A magnificent sight can cover most of the sky.
The beginning of the phenomenon
Aurora begins with the appearance of a light band. Rays come out of it. The brightness may increase. The area of the sky covered by the miraculous phenomenon is increasing. The height of the rays of light, falling closer to the surface of the Earth, also increases.
Bright flashes and play of color delight observers. The movements of the waves of light are mesmerizing. This phenomenon is associated with the activity of the Sun, the source of light and heat.
What is this
Aurora is a rapidly changing glow of the upper rarefied layers of air in certain parts of the night sky. This phenomenon, along with the sunrise, is sometimes referred to as the aurora. During the day, the light show is not visible, but the devices record the flow of charged particles at any time of the day.
Causes of the aurora
Magnificent natural phenomenonarises due to the Sun and the presence of the atmosphere of the planet. For the formation of the aurora also requires the presence of a geomagnetic field.
The sun is constantly ejecting charged particles from itself. A solar flare is a factor due to which electrons and protons enter outer space. They fly at high speed towards the rotating planets. This phenomenon is called the solar wind. It could be dangerous for all life on our planet. The magnetic field protects the Earth's surface from solar wind penetration. It sends charged particles to the poles of the planet, according to the location of the geomagnetic field lines. However, in the case of more powerful flares on the Sun, the population of the Earth observes auroras in temperate latitudes. This happens if the magnetic field does not have time to send a large stream of charged particles to the poles.
The solar wind interacts with the molecules and atoms of the planet's atmosphere. This is what causes the glow. The greater the number of charged particles that reached the Earth, the brighter the glow of the upper layers of the atmosphere: the thermosphere and exosphere. Sometimes even the mesosphere - the middle layer of the atmosphere - reaches the particles of the solar wind.
Aurora types
Types of auroras are different and can smoothly transition from one to another. Light spots, rays and stripes, as well as coronas are observed. The aurora borealis can be almost stationary or streaming, which is especially mesmerizing for observers.
Aurora Earth
There is a rather powerful geomagnetic field on our planet. It is strong enough toconstantly send charged particles towards the poles. That is why we can observe a bright glow on the territory of the band, where the isochasm of the most frequent auroras passes. Their brightness directly depends on the work of the geomagnetic field.
The atmosphere of our planet is rich in various chemical elements. This explains the different colors of the sky glow. So, an oxygen molecule at an altitude of 80 kilometers, when interacting with a charged particle of the solar wind, gives a pale green color. At an altitude of 300 kilometers above the Earth, the color will be red. The nitrogen molecule exhibits a blue or bright red color. In the photo of the aurora, bands of different colors are clearly distinguishable.
The northern lights are brighter than the southern lights. Because protons are moving towards the north magnetic pole. They are heavier than the electrons rushing towards the south magnetic pole. The glow produced by the interaction of protons with the molecules of the atmosphere is somewhat brighter.
The device of the planet Earth
Where does the geomagnetic field come from, protecting all life from the destructive solar wind and moving charged particles towards the poles? Scientists believe that the center of our planet is filled with iron, which is molten from heat. That is, iron is liquid and is constantly in motion. From this movement, electricity and the planet's magnetic field arise. However, in some parts of the atmosphere, the magnetic field weakens for some unknown reason. This happens, for example, over the southern part of the Atlanticocean. Here, only a third of the magnetic field from the norm. This worries scientists because the field continues to weaken at the present time. Experts have calculated that over the past 150 years, the Earth's geomagnetic field has weakened by another ten percent.
Area where natural phenomena occur
Zones of polar lights do not have clear boundaries. However, the brightest and most frequent are those that appear as a ring near the Arctic Circle. In the Northern Hemisphere, you can draw a line on which the auroras are the strongest: the northern part of Norway - the islands of Novaya Zemlya - the Taimyr Peninsula - the north of Alaska - Canada - the south of Greenland. At this latitude - about 67 degrees - the auroras are observed almost every night.
The peak of phenomena often occurs at 23:00. The brightest and longest lights are on the equinoxes and dates close to them.
More often auroras occur in areas of magnetic anomalies. Here their brightness is higher. The greatest activity of the phenomenon is observed on the territory of the East Siberian magnetic anomaly.
Glow appearance height
Typically, about 90 percent of all aurorae occur between 90 and 130 kilometers. Auroras were recorded at an altitude of 60 kilometers. The maximum recorded figure is 1130 kilometers from the Earth's surface. At different heights, different forms of glow are observed.
Features of a natural phenomenon
A number of unknown dependences of the beauty of the northern lights on some factors were discovered by observers and confirmed by scientists:
- Polar lights,emerging over sea space are more mobile than those occurring over land.
- There is less glow over small islands, as well as over desalinated water, even in the middle of the sea surface.
- Above the coastline, the phenomenon is observed much lower. Towards the land, as well as towards the ocean, the height of the aurora increases.
The speed of the charged particles of the Sun
The distance from the Earth to the Sun is about 150 million kilometers. Light reaches our planet in 8 minutes. The solar wind moves more slowly. From the moment scientists notice a solar flare, more than a day must pass before the aurora begins. On September 6, 2017, experts noticed a powerful solar flare and warned Muscovites that on September 8, the northern lights might be visible in the capital. Thus, the forecast of an impressive natural phenomenon is possible, but only in a day or two. In which region the radiance will appear brighter, no one can predict with accuracy.
What is isochasm
Specialists put on the map of the earth's surface points with marks of the frequency of occurrence of auroras. Connected by lines points with a similar frequency. So we got isochasms - lines of equal frequency of occurrence of auroras. Let us describe once again the isochasm of the highest frequency, but relying on some other objects of the area: Alaska - Great Bear Lake - Hudson Bay - south of Greenland - Iceland - north of Norway - north of Siberia.
The farther from the main isochasm of the Northern Hemisphere, the less auroras occur. For example, in St. Petersburg, the phenomenon can be observed about once a month. And at the latitude of Moscow - once every few years.
Earth's magnetic pole
The magnetic pole of the Earth does not coincide with the geographic pole. It is located in the northwestern part of Greenland. Here, the northern lights occur much less frequently than in the band of the highest frequency of the phenomenon: only about 5-10 times a year. Thus, if the observer is located to the north of the main isochasm, then he sees auroras more often in the southern side of the sky. If a person is located south of this band, then the aurora is more often manifested in the north. This is typical for the Northern Hemisphere. For the South - exactly the opposite.
On the territory of the North Geographic Pole, auroras occur about 30 times a year. Conclusion: you do not need to go to the most severe conditions to enjoy a natural phenomenon. In the main isochasm band, the glow repeats almost every day.
Why do the northern lights sometimes have no color
Travelers sometimes get upset when they fail to catch a colorful light show during their stay in the north or south. People can often observe only a glow that has no color. This is not due to the peculiarity of a natural phenomenon. The fact is that the human eye is not able to capture colors in low light. In a gloomy room, we see everything in black and white. The same thing happens when observing a natural phenomenon in the sky: if it is not bright enough, then our eyes will not pick up colors.
Specialists measure the brightness of the glow in points from one to four. Only three- and four-magnitude auroras appear colored. The fourth degree is close in brightness to moonlight in the night sky.
Cycles of solar activity
The emergence of the aurora is always associated with solar flares. Once every 11 years, the activity of the luminary increases. This always leads to an increase in the intensity of the auroras.
Northern lights over the planets of the solar system
Aurora is not only on our planet. Earth's auroras are bright and beautiful, but Jupiter's phenomena are brighter than Earth's. Because the magnetic field of the giant planet is several times stronger. It sends the solar wind in opposite directions even more productively. All light accumulates in certain areas near the planet's magnetic poles.
Jupiter's moons affect the aurora. Especially Io. Behind it is a bright light, because the natural phenomenon follows the direction of the magnetic field lines. In the photo - the aurora in the atmosphere of the planet Jupiter. The bright band left by Io's moon is clearly visible.
Auroras have also been discovered on Saturn, Uranus, Neptune. Only Venus has almost no magnetic field of its own. Flashes of light arising from the interaction of the solar wind with the atoms and molecules of the atmosphere of Venus are special. They cover the entire atmosphere of the planet entirely. Moreover, the solar wind reaches the surface of Venus. However, such lights are never bright. Charged particles of the solar windnowhere accumulate in large numbers. From space, Venus looks like a faintly luminous ball when attacked by charged particles.
Geomagnetic disturbance
The solar wind is trying to break through our planet's magnetosphere. The geomagnetic field in this case does not remain calm. There are disturbances on it. Each person has their own electric and magnetic fields. It is these fields that are affected by the resulting perturbations. This is felt by people all over the planet, especially those with poor he alth. People with good he alth do not notice such an impact. During the attack of charged particles, sensitive people may have a headache. But it is the solar wind that is the necessary factor for the occurrence of auroras.
Attitude of peoples to a natural phenomenon
Usually the locals associated the aurora borealis with something not very good. Perhaps because geomagnetic storms have a bad effect on people's well-being. The radiance itself does not pose any danger.
Inhabitants of the more southern regions, not used to such phenomena, felt something mysterious when bright flashes appeared in the sky.
Currently, residents of temperate and more southern latitudes are eager to see this miracle of nature. Tourists travel to the North or to the Antarctic Circle. They do not wait for the phenomenon to be observed at their native latitude.
Aurora Borealis is an enchanting natural phenomenon. It is unusual for residents of warm regions and familiar to the population of the tundra. It often happens that forin order to learn something new, you need to go on a journey.
