What Is the Aurora Australis?

Aurora is a gorgeous and colorful plasma phenomenon, which occurs because the sun's charged particle current (solar wind) enters the Earth's magnetic field. It appears at night in the high altitudes near the north and south poles of the earth. It is called Antarctic in the South Pole, and it is called Northern Light in the North Pole. The aurora of the earth is generated by the high-energy charged particle flow (solar wind) from the Earth's magnetosphere or the sun, which excites (or ionizes) molecules or atoms in the upper atmosphere.

According to research on the distribution of aurora, the shape of the aurora region is not based on

due to

Aurora can be divided into two types: diffuse aurora and discrete aurora. Even in the dark sky, the naked eye may not see the diffuse aurora gleam and shape diffused in the sky, but it defines the range of the aurora band. Discrete aurora is the part that can clearly see the shape in the almost invisible diffuse aurora. They can be easily seen by the naked eye. The brightest is enough to read books and newspapers at night. But the discrete aurora can only be seen in the night sky, because its brightness is not enough to show up in the sun. Aurora is usually a diffuse spot or arc when it appears in the aurora zone ^[16]

Aurora appears over the planet's high magnetic latitudes and is a gorgeous and colorful luminous phenomenon. And the aurora of the earth comes from the earth

Most of the aurora occurred 90 to 130 kilometers above the earth. United States

Aurora is an atmospheric luminous phenomenon unique to the north and south poles. Aurora has left a beautiful figure in the myths and legends of both the East and the West. The development of modern science has enabled humans to look at Aurora with a rational eye and make scientific explanations for it.

For a long time, the cause of the aurora has not been satisfactorily explained. For quite some time, people have thought that the aurora may be formed by the following three reasons. One view is that the aurora is a fire that ignites outside the earth. Because the Arctic is near the edge of the earth, it can be seen. Another view is that the aurora is a glow that reflects after the sun has sunk to the west. Another view is that polar ice is rich in snow and ice. They absorb sunlight during the day, store it, and release it at night to become aurora. In short, there are many opinions, and there is no certain theory. Until 20

Aurora landscape captured by Danish photographer in the early morning on August 4

In the 1960s, a combination of ground observations and satellite and rocket-detected data was used to study the physical description of the aurora.

It is recognized that the aurora is related to the large-scale interaction of the Earth's upper atmosphere and the geomagnetic field on the one hand, and on the other hand to the high-speed charged particle stream emitted by the sun, which is commonly referred to as the solar wind. It can be seen that the indispensable conditions for the formation of aurora are the atmosphere, magnetic field and solar wind. Other planets in the solar system that meet these three conditions, such as Jupiter and Mercury, will also produce aurora around them, which has been proved by actual observation.

The geomagnetic field is distributed around the earth and is surrounded by the solar wind to form a mallet-like colloid. Its scientific name is called the magnetosphere. In order to be more visual, let's make an analogy. The magnetosphere can be regarded as a huge television picture tube, which gathers the solar wind particle stream entering the high-altitude atmosphere into a beam and focuses on the polar region of the geomagnetism, which is the phosphor screen of the picture tube, and the aurora is moved on the TV screen. image. However, the TV screen here is not 18 inches or 24 inches, but a polar high-altitude atmosphere with a diameter of 4,000 kilometers.

Aurora landscape captured by Danish photographer in the early morning on August 4 ^[22]

. Usually, the audience on the ground can only see 1/50 of the picture somewhere. In a television picture tube, an electron beam hits the television screen, because the screen is coated with a luminescent substance, which emits light and displays an image. Similarly, when an electron beam from space penetrates into the upper atmosphere of the polar region, it will excite the molecules and atoms in the atmosphere and cause light emission, and people will see the aurora image display. In a television picture tube, a pair of electrodes and an electromagnet act on an electron beam to produce and form a moving image. When the aurora occurs, the display and movement of the aurora is caused by the particle beam being modulated by the changes in the electric and magnetic fields in the magnetic layer.

Aurora is not only an optical phenomenon, but also a radio phenomenon. It can be detected by radar and it also emits some radio waves. Some people also say that Aurora can make all kinds of sounds. Aurora is not only an important subject of scientific research, it also directly affects many practical engineering projects such as radio communications, long cable communications, and long pipelines and power transmission lines. Aurora can also affect climate and biological processes. Of course, Aurora also has many unsolved mysteries.

The aurora is caused by the impact of high-energy particles (electrons and protons) from outside the atmosphere on atoms in the upper atmosphere. This interaction often occurs in areas around the Earth's magnetic poles. As a part of the solar wind, the charged particles are captured by the Earth's magnetic field when they reach the vicinity of the earth, and they are caused to fall toward the magnetic poles. They collide with atoms of oxygen and nitrogen, knocking off electrons and making them excited ions. These ions emit radiation of different wavelengths, producing aurora characteristic colors such as red, green or blue. During the height of solar activity, the aurora sometimes extends to mid-latitudes. For example, in the United States, northern lights have been seen at 40 degrees north to south. Aurora has a variety of shapes such as curtain-shaped, arc-shaped, band-shaped and ray-shaped. The arc-shaped aurora with uniform light emission is the most stable shape, and it can sometimes stay for several hours without noticeable changes. However, most other shapes of aurora usually show rapid changes. The lower edge of the arc and folded aurora is usually more pronounced than the upper end. The aurora eventually retreated toward the polar pole, and the glow rays gradually disappeared into the diffused white light sky. The mechanism that causes the dynamic changes of the aurora is still fully understood. One of the forms of energy created by the sun, such as light and heat, is called "solar wind". This is a powerful stream of charged subatomic particles that can cover the earth. The solar wind flows around the earth and hits the earth's magnetic field at a speed of about 400 kilometers per second. The magnetic field makes the particle flow deviate to the geomagnetic poles, causing charged particles It reacts with the upper atmosphere of the earth to form aurora. Antarctica is formed in the Antarctic area. This phenomenon is also seen in the Arctic and is commonly referred to as the Northern Lights.

Aurora pictures ^[23]

Scientists have learned that the Earth's magnetic field is not symmetrical. Under the blowing of the solar wind, it has become some kind of "streamline". That is to say, the magnetic lines of force facing the sun are greatly compressed, but a long, magnetic tail similar to a comet tail is pulled out in the opposite direction. The length of the magnetic tail is at least 1,000 Earth radii. When the solar activity undergoes drastic changes (such as flare bursts), it often causes sub-storms in the Earth's magnetosphere.

Linda Drake, 40, has taken many beautiful pictures of the Northern Lights over the past 4 years. Every year, she comes to Manitoba, Canada at a temperature of minus 20 degrees, in order to capture the most awesome aurora pictures. Figure right

The study was hosted by Angelo Polos of the University of California, Los Angeles, and the results were presented at a conference of the American Geophysical Union on December 9, 2007.

The aurora observed in the northern hemisphere is called the Northern Lights, and the aurora observed in the southern hemisphere is called the South Aurora. It often appears in two ring-shaped areas near 67 degrees north and south latitudes. There are more than 200 days of aurora over the year ^[24] .

On June 13, 2017, the research team of the National Polar Institute of Japan and the University of Tokyo, Kyoto University, and Nagoya University announced that using high-performance cameras, it successfully took high-speed flashing aurora images over 3 years. The special aurora that repeatedly appears bright and dark in a short time is produced under the action of hydrogen ions. It is expected that this research will further unravel the mystery of the occurrence of aurora. ^[25]