What are these lights called

Aurora borealis

The sun flings matter into space

The red glowing ball appears calm and romantic when it slowly sinks over the sea. It is difficult to imagine the complex physical processes that take place on the sun. In addition to light and thermal radiation, huge amounts of matter are constantly evaporated from the sun or thrown into space by eruptions. Scientists speak of the so-called solar wind.

This solar wind consists mainly of protons and electrons and reaches the earth in an interval of about one to three days. It would make life on earth impossible if we weren't protected from particle bombardment and radiation by the atmosphere and especially by the earth's magnetic field.

Violent eruptions occur again and again in the shell of the sun, especially at times of maximum solar activity. The solar wind turns into a real storm during such eruptions. Several billion tons of hot gas escape.

The speed of the solar wind can vary greatly: while the normal solar wind is around 300 kilometers per second, such a hurricane gust rushes through space much more rapidly. In this way, the particles can reach the earth in the form of a shock wave after just 24 hours.

Fascinating northern lights indicate a solar storm, which is characterized by a solar wind speed greater than 300 kilometers per second. It can even go as fast as 700 kilometers per second.

In strong solar storms, higher speeds were also measured, such as 2000 kilometers per second during the storm in October 2003.

Impact on the Earth's magnetic field

The pressure of the solar wind is so strong that it deforms the magnetic field of our earth. On the day side of the earth it is compressed. On the night side, it protrudes several million kilometers into space.

As the solar wind approaches the magnetic field, it is gradually diverted from it and flows around the earth. Charged particles from the solar wind are captured.

As in a giant electricity generator, the kinetic energy of the particles passing by is converted into electrical energy at the boundary layer between the geomagnetic region and the solar wind.

The electrical voltage arises from the fact that the charged particles of the solar wind - the positive protons and the negative electrons - are separated in the earth's magnetic force field. As a result, a huge electrical voltage builds up over the earth.

This voltage is partially discharged by the fact that a stream of electrons flows in spirals along the field lines towards the earth, namely to the point where the field lines enter and exit. The huge confluences for the magnetic field lines are the polar regions.

The electrons of the solar wind collide with molecules in the atmosphere about 150 kilometers from Earth. There is a lively exchange of energy. The molecules are electrically and energetically charged and thus stimulated to glow.

One result of this are the northern lights at the north and south poles. During solar storms, this phenomenon is not limited to the polar regions, so that we can also observe the northern lights in the northern night sky.

Northern lights can take on six colors

The usual colors of the northern lights are red, green and blue. This then results in mixed colors such as purple, white and sometimes yellow. The colors that emerge depend on the various components of the atmosphere and also on the height at which the spectacle takes place.

Green auroras are usually caused by oxygen at an altitude of around 80 to 150 kilometers. At an altitude of between 150 and 600 kilometers, nitrogen atoms create red and blue colors.

Sometimes they interfere with radio signals

These colorful spectacles can also have a negative impact, for example on the functioning of research and communication satellites. Strong tension fields falsify measurement data or signals to earth. Electric currents of several thousand amperes have already been measured in the Alaska pipeline due to the effects of the aurora borealis.

Radio, radio and satellite navigation are disrupted. Or even entire power grids fail, as in 1989 during a sunspot maximum. At that time, a central transformer station burned down in Canada and a chain reaction resulted in a blackout throughout the northeast - the residents had no electricity for hours or even days.

There are also northern lights in Germany

The name says it all: Northern lights are particularly tied to the polar regions. They mostly appear in a belt around the magnetic pole. Accordingly, the northern lights are then also referred to as "northern lights" or "southern lights".

The Northern Lights zone runs over northern Scandinavia, Iceland, the southern tip of Greenland, northern Canada, Alaska and the northern coast of Siberia. In the Antarctic and the sea areas around it, the northern lights shine as "southern lights".

In the polar regions you can see the northern lights almost every clear night. The best time is between the beginning of September and mid-April. In summer, the colorful play of light can hardly be seen, because at this time the sky is too bright.

The further the geographical latitude decreases, the rarer the heavenly natural spectacle becomes. In our latitudes, the northern lights are seldom seen. But during solar storms, i.e. maximum solar activity, we can admire the northern lights about four to eight times a year, even over Germany.