Aurora is one of the many wonders of nature. It can be observed in Russia. In the north of our country, a strip passes 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 depart from her. Brightness may increase. The area of the sky, covered by a wonderful phenomenon, is increasing. The height of the rays of light descending closer to the surface of the Earth also increases.
Bright flashes and overflows of color delight observers. The movements of the waves of light are fascinating. This phenomenon is associated with the activity of the Sun - a source of light and heat.
What it is
Aurora is called the rapidly changing glow of the upper rarefied layers of air in individual parts of the night sky. This phenomenon, along with sunrise, is sometimes referred to as Aurora. The day of the light show is not visible, however, the instruments record the flow of charged particles at any time of the day.
Causes of Aurora Borealis
A magnificent natural phenomenon occurs due to the sun and the presence of the atmosphere of the planet. The formation of auroras also requires the presence of a geomagnetic field.
The sun constantly throws out charged particles. A flash on the Sun is a factor due to which electrons and protons enter outer space. They fly with great speed towards the rotating planets. This phenomenon is called the solar wind. It could be dangerous for all living things on our planet. A magnetic field protects the Earth's surface from the penetration of the solar wind. It sends charged particles to the poles of the planet, according to the location of the lines of force of the geomagnetic field. However, in the case of more powerful flares on the Sun, the Earth's population 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 causes a glow. The larger the number of charged particles reaching the Earth, the brighter is the glow of the upper atmosphere: the thermosphere and exosphere. Sometimes the particles of the solar wind reach the mesosphere - the middle layer of the atmosphere.
Types of Aurora
Types of auroras are different and can smoothly pass one into another. There are light spots, rays and stripes, as well as crowns. Aurora borealis can be almost motionless or flowing, which is especially fascinating for observers.
Earth auroras
There is a rather powerful geomagnetic field on our planet. It is strong enough to constantly send charged particles toward the poles. That is why we can observe a bright glow in the territory of the strip 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 heavenly 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.
Northern lights are brighter than southern ones. Because protons are moving toward the north magnetic pole. They are heavier than electrons rushing towards the south magnetic pole. The radiance resulting from the interaction of protons with atmospheric molecules 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 constantly in motion. This movement gives rise to electricity and the magnetic field of the planet. 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 Atlantic Ocean. Here, only a third of the magnetic field is normal. This worries scientists, because the field continues to weaken at the present time. Experts estimate that over the past 150 years, the earth's geomagnetic field has weakened another ten percent.
Area of occurrence of a natural phenomenon
Zones of auroras do not have clear boundaries. However, the most striking and frequent are those that appear as a ring at the polar circle. In the Northern Hemisphere, you can draw a line on which the auroras are the strongest: the northern part of Norway - the Novaya Zemlya Islands - the Taimyr Peninsula - the north of Alaska - Canada - the south of Greenland. At this latitude - about 67 degrees - auroras are observed almost every night.
The peak of occurrence most often occurs at 23:00. The brightest and longest auroras are on the days of the equinox 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 height
As a rule, about 90 percent of all auroras occur at an altitude of 90 to 130 kilometers. Registered auroras at an altitude of 60 kilometers. The maximum recorded figure is 1130 kilometers from the surface of the Earth. At different heights, different forms of glow are observed.
Features of the natural phenomenon
A number of unknown dependences of the beauty of the northern lights on certain factors were discovered by observers and scientists confirmed:
- Auroras that arise over the sea are more mobile than those that appear over land.
- Less luminescence over small islands, as well as over desalinated water, even located in the middle of the sea surface.
- Over the coastline, the phenomenon is much lower. Towards the land, as well as towards the ocean, the height of the aurora increases.
The speed of flight of 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 flash on the Sun and warned Muscovites that on September 8, perhaps, the northern lights will be noticeable in the capital. Thus, a 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
Experts put dots on the map of the earth's surface with notes on the frequency of occurrence of auroras. Connected the lines with points with a similar frequency. This is how isochasms turned out - lines of equal frequency of auroras. Once again we describe the isochasm of the highest frequency, but relying on some other objects of the area: Alaska - Big 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 often the auroras occur. For example, in St. Petersburg the phenomenon can be observed approximately once a month. And at the latitude of Moscow - once every few years.
Earth's magnetic pole
The Earth’s magnetic pole does not coincide with the geographic pole. It is located in the northwestern part of Greenland. Here the northern lights happen 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 north of the main isochasm, then he often sees auroras in the southern side of the sky. If a person is located south of this strip, then the aurora often appears in the north. This is characteristic of the Northern Hemisphere. For the South - exactly the opposite.
Auroras occur about 30 times a year on the territory of the North Geographic Pole. Conclusion: no need to go to the most severe conditions to enjoy the natural phenomenon. In the band of the main isochasm, the glow is repeated almost every day.
Why the northern lights sometimes do not have color
Travelers are sometimes upset if they fail to catch a color light show during their stay in the north or south. People often can only observe a glow that has no color. This is not due to the nature of the phenomenon. The fact is that the human eye is not able to pick up colors in low light. In the gloomy room we see all objects 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.
Experts measure the brightness of the glow in points from one to four. Only three- and four-point auroras seem colored. The fourth degree is close in brightness to moonlight in the night sky.
Solar Activity Cycles
The occurrence of aurora is always associated with flares on the sun. Every 11 years, the activity of the star increases. This always leads to an increase in the intensity of auroras.
Aurora borealis over the planets of the solar system
Not only on our planet auroras arise. The auroras of the Earth are bright and beautiful, but on Jupiter, the phenomena exceed the brightness of the earth. Because the magnetic field of a giant planet is several times stronger. It sends the solar wind in opposite directions even more productively. All light accumulates in certain areas at the magnetic poles of the planet.
The moons of Jupiter affect the aurora. Especially Jo. A bright light remains behind it, because a natural phenomenon follows the direction of the magnetic field lines. In the photo - aurora in the atmosphere of the planet Jupiter. The bright band left by Io’s satellite is clearly visible.
On Saturn, Uranus, Neptune, auroras were also found. Only Venus has almost no magnetic field. The 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 as a whole. Moreover, the solar wind reaches the surface of Venus. However, such auroras are never bright. Charged particles of the solar wind never accumulate in large quantities. From space, Venus, when attacked by charged particles, looks like a faintly luminous ball.
Perturbation of the geomagnetic field
The solar wind is trying to break through the magnetosphere of our planet. The geomagnetic field in this case does not remain calm. Disturbances occur on it. Each person has his own electric and magnetic fields. It is these fields that are affected by the perturbations that arise. This is felt by people all over the planet, especially those with poor health. People with good health do not notice this effect. Sensitive people may have a headache during an attack of charged particles. But it is the solar wind that is the necessary factor for the occurrence of auroras.
The attitude of peoples to a natural phenomenon
Usually locals associated the aurora with something not very kind. Perhaps because geomagnetic storms have a bad effect on people's well-being. Radiance itself does not carry any danger.
Residents of more southern areas, not accustomed to such phenomena, felt something mysterious when light flashes appeared in the sky.
Currently, residents of temperate and more southern latitudes seek to see this natural wonder. Tourists travel to the North or to the Arctic Circle. They do not wait for the phenomenon to be observed at their native latitude.
Aurora 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 in order to learn something new, you need to go on a trip.