How are the Northern Lights and the Southern Lights formed?

In fact, the formation principle of the Southern Aurora and the Northern Lights is the same, just the difference in geographical location, so there is no need to explain them separately, let's talk about them in a unified way.

The formation of the Southern and Northern Lights can be explained in one sentence: that is, the luminescence of plasma in the Earth's magnetic field.

Plasma, this term is not unfamiliar to everyone. Plasma TV, which was popular for a while a few years ago, brought this concept into everyone's sight. But what the hell is plasma?

We know that an object generally has three states: solid, liquid, and gas. Plasma is the fourth state of an object's existence!

For example, water is a liquid, frozen solid ice, and when heated, it turns into gas.

If the water vapor is heated to a high enough temperature, the water molecules in it will be broken down into freely moving hydrogen and oxygen atoms, and then a small amount of heat will be given, and the ionization process will take place, and the negatively charged electrons will escape from the atoms, leaving behind positively charged ions.

This mixture of ions, which can move freely and have positive and negative charges, is plasma. In fact, at a sufficiently high temperature, any gas can be converted into plasma.

Now that we know what plasma is, it's easy to explain why auroras are formed.

As we know, the earth is a large magnetic field, and the south pole and the north pole are the south and north poles of the earth respectively. In addition to emitting light, the sun also emits a large amount of plasma, which travels through the vast space to the earth and enters the earth's magnetic field.

Because the plasma is charged, it will be accelerated in the magnetic field and converge towards the south pole and the north pole, and the plasma traveling at high speed collides with various ions in the atmosphere to emit various lights, and because the plasma is concentrated in large quantities at the south pole and the north pole, the aurora can only be seen near the south pole and the north pole.

Auroras are coloured luminescence phenomena that often occur in the atmosphere above regions near the geomagnetic poles at latitudes. Auroras are generally ribbon-shaped, arc-shaped, curtain-shaped, and radial, and these shapes are sometimes stable and sometimes change continuously. The principle of the generation of auroras and the distribution area of auroras:

Auroras are produced by the excitation or ionization of molecules or atoms in the upper atmosphere by a stream of charged energetic particles (up to 10,000 electron volts) from a sun-active region. Due to the geomagnetic field, these energetic particles are turned to the polar regions, so auroras are commonly found in high magnetic latitudes. Auroras often occur in the range of about 25° to 30° from the magnetic pole, and this area is called the aurora zone.

The region between 45° and 60° of geomagnetic latitude is called the weak aurora zone, and the area of the geomagnetic latitude below 45° is called the micro aurora zone. The height of the lower boundary of the aurora is less than 100 kilometers above the ground, the height of the maximum luminous place is about 110 kilometers above the ground, and the normal maximum boundary is about 300 kilometers above the ground, and in extreme cases, it can reach more than 1,000 kilometers. According to the study of the distribution of auroras, the shape of the auroral region is not a ring centered on the geomagnetic pole, but an oval shape.

The spectral line range of the aurora is about 3100 6700 angstroms, of which the most important spectral line is the 5577 angstroms oxygen atom green line, which is called the aurora green line. As early as 2,000 years ago, China began to observe the aurora, and there are rich records of the aurora. The aurora is diverse, colorful, and beautiful in shape, and there is no phenomenon in nature that can compare with it.

It is difficult for any colored pen to paint the dazzling light that frolicks and changes in the cold polar air. Sometimes the aurora appears for a very short time, like a festive firework flashing in the sky and disappearing without a trace; Sometimes it can shine in the sky for hours; Sometimes it's like a streamer, sometimes it's like a flame, sometimes it's like a huge screen full of colors, as if a full-dome movie is being shown, giving people a visual aesthetic enjoyment. <>

Aurora is an atmospheric luminescence phenomenon unique to the Arctic and Antarctic regions. The development of modern science has enabled human beings to look at the aurora with a rational eye and make a scientific explanation for it. For a long time, the mechanism of aurora formation has not been satisfactorily explained.

For quite some time, it was thought that the aurora could be formed by three reasons. One view is that the aurora is a fire that has been ignited outside the Earth, and that it can be seen because the Arctic region is close to the edge of the Earth. Another view is that the aurora is a glow reflected by the red sun after the sun has sunset.

There is also a belief that the polar regions are rich in ice and snow, and they absorb sunlight during the day, store it, and release it at night, which becomes the aurora. In short, there are different opinions, and there is no definite opinion. It was not until the 60s of the 20th century that the physical description of the aurora was gradually formed by combining the ground observations with the data detected by satellites and rockets.

The cause of this is the action of energetic particles (electrons and protons) from outside the atmosphere that hit atoms in the upper atmosphere. This interaction often occurs in the region around the Earth's magnetic poles. It is now known that charged particles, which are part of the solar wind, are captured by the Earth's magnetic field when they reach the vicinity of the Earth and cause them to fall towards the magnetic poles.

They collide with atoms of oxygen and nitrogen, knocking away electrons and turning them into excited ions, which emit radiation of different wavelengths to produce the characteristic colors of the aurora of red, green, or blue. At the height of solar activity, the aurora sometimes extends into the mid-latitudes, for example, in the United States, where the Northern Lights have been seen from 40 degrees north to south. Auroras come in a variety of shapes such as glowing curtains, arcs, bands, and rays.

The evenly glowing aurora is the most stable shape and sometimes lingers for hours without noticeable changes. However, most other shapes of aurora usually always show rapid changes. The lower edge of the curved and folded auroras are usually more pronounced than the upper ends.

The aurora eventually receded towards the earth's poles, and the glow rays gradually disappeared into the diffuse white light sky. The mechanism that causes the dynamic changes in the aurora is still fully understood.

Among the forms of energy created by the sun, such as light and heat, there is one type of energy that is called"Solar wind"。This is a powerful stream of charged subatomic particles that can cover the Earth, and this solar wind flows around the Earth above the Earth, hitting the Earth's magnetic field at a speed of about 400 kilometers per second, and the magnetic field deflects the flow of particles towards the Earth's magnetic poles, causing the charged particles to chemically react with the Earth's upper atmosphere to form auroras. The formation in the Antarctic region is called the Australis Aurora.

This phenomenon can also be seen in the Arctic region, commonly known as the Northern Lights.

Auroras are caused by a stream of charged particles from the sun entering the earth's magnetic field and converging high in the sky near the north and south poles of the earth.

Auroras often appear in the sky above the geomagnetic pole at latitude, generally in the form of bands, arcs, curtains, and radials, and these shapes are sometimes stable and sometimes change continuously. There are three conditions for the formation of auroras: the atmosphere, the magnetic field, and high-energy charged particles.

Features of the Northern Lights

1. Diversity.

The aurora borealis is characterized by its diversity and is regarded as one of the most beautiful wonders in nature. It is colorful, different shapes, and incomparably beautiful, which is due to the fact that the high-altitude body is composed of a variety of elements, and the color of the light emitted by the gas of different elements that are bombarded is different, so the aurora is gorgeous and colorful, and the changes are endless. Sometimes it appears for a very short time, like a festive firework flashing in the air and disappearing without a trace; Sometimes it can be in the air for hours.

2. Appearance time.

The most likely period for the occurrence of aurora is before the spring and autumn equinoxes, and the frequency of occurrence in spring and autumn is more frequent than in summer and winter. In addition, the frequency and brightness of auroras also increase when there are many sunspots or when the solar cycle is in a phase when coronal ejections increase and the solar wind intensifies.

Categories: Science & Engineering Belt.

Analysis: 1) The convergence effect caused by the deflection of the electrons coming from the sun approaching the geomagnetic field and the concentration of the magnetic poles in a spiral. In order to pass through the discharge of the extremely thin and coldest layer of the high atmosphere, it causes a magnificent luminescence phenomenon in the atmosphere.

The shape has arches, bars and mist, etc., and the states range from beating, flickering to **. Auroras are usually white to green, red, yellow, blue, purple or pink in color and last from a few hours to a few days.

2) Why do the auroras only appear at the poles of the earth? It turns out that the earth has a strong magnetic field, and the charged particles from the sun are affected by the earth's magnetic field, due to the effect of the convergence of magnetic field lines, the gas composed of these electrons and positive ions (we call it plasma) will produce an upward electric field along the direction of the earth's magnetic field line, so the electrons in the plasma are accelerated by this electric field and enter the ionosphere at high latitudes, so only the charged particles that shoot into the polar regions can enter the upper atmosphere to produce auroras.

3) The geomagnetic north pole is in Canada (the geomagnetic north pole is about 1200km away from the geographical north pole. The two are intersected by the center of the earth. Therefore, aurora is common in southern Canada and the northern United States, and is rarely seen in the low magnetic latitudes of Siberian volta.

The Northern Lights can usually only be seen at higher magnetic latitudes, but can be seen at slightly lower magnetic latitudes when solar storms are intense. Scientists have been able to correctly ** the 11-year cycle of solar storms, a large number of charged particles from the solar storm rush to the earth, and interact with the geomagnetic field to produce the gorgeous scenery of the Northern Lights. The second millennium AD coincided with the peak of the 11-year cycle, which can also be seen at slightly lower magnetic latitudes.

4) The one located at the North Pole is called the Northern Lights, and the one located at the South Pole is called the South Lights, just like the halo on the head of an angel, set in the night sky of the North and South Poles of the earth. The Northern Lights and Southern Lights can sometimes appear in pairs like images in a mirror.