Formation principle of aurora

Aurora is a large-scale discharge process around the earth. Charged particles from the sun arrive near the earth, and the earth's magnetic field forces some of them to concentrate along the magnetic field lines to the North and South poles. When they enter the polar upper atmosphere, they collide and excite with atoms and molecules in the atmosphere, producing light and forming aurora.

Aurora appears in the high magnetic latitudes of the earth, which is a rare natural landscape. Aurora not only appears on the earth, but also on other planets with magnetic fields in the solar system. So how is the aurora formed?

At high altitudes near the North and South poles of the earth, a strange light often appears at night. It is colorful: purple, rose, orange, white and blue.

Its shapes are also very different: some are like ribbons flying in the air, some are like beating flames, some are like curtains, some are like soft silk, and some are like huge umbrellas. This natural scene of "the fire tree and the silver flowers are sleepless" is the aurora.

Early point of view

1, Benjamin Franklin's theory: The magical Northern Lights are caused by thick charged particles in the polar regions, strong snow and other moisture.

2. The electrons of aurora come from the light beam emitted by the sun. This was put forward by Christian Berklein in 1900. She uses a vacuum chamber and a magnetized earth model in the laboratory to show how electrons are guided to the polar regions. The problems of this model include the lack of aurora in polar regions, the negative charge itself scattering these beams, and the lack of any observation evidence in space.

3. Broken barrel theory: Aurora is an overflow radiation belt, which was first put forward by james van allen and his colleagues in about 1962. They pointed out that the huge energy gained in the radiation area will soon be exhausted in the spread of aurora. Soon after, it was obvious that all the positively charged ions trapped in the radiation belt were high energy, while almost all the electrons in the aurora were low energy.

Aurora is caused by the particles in the solar wind being guided to the top of the atmosphere by the earth's magnetic field lines. This applies to the tip of the aurora, but outside the tip, the solar wind has no direct influence. On the other hand, the energy of solar wind mainly stays in positively charged ions, and the electron is only 0.5eV, but it will rise to 50 ~ 100 EV at the cusp, which is still far lower than the energy of aurora.

Modern viewpoint

Aurora is a large-scale discharge process around the earth. Charged particles from the sun arrive near the earth, and the earth's magnetic field forces some of them to concentrate along the magnetic field lines to the North and South poles. When they enter the polar upper atmosphere, they collide and excite with atoms and molecules in the atmosphere, producing light and forming aurora.

According to the data sent back by NASA's Simis mission, scientists found that charged particles released by the sun flew to the earth like airflow, and when they hit the magnetic field over the North Pole, they formed some distorted magnetic fields.

The energy of charged particles is released in an instant in the form of bright and dazzling northern lights, and the reason why the aurora of the earth is mainly red and green is because the nitrogen atoms and oxygen atoms in the thermal stratification are shattered by electrons, giving off red and green light respectively.

The research was conducted by Angie Polos of UCLA, and the results were presented at the academic meeting of American Geophysical Union on February 9, 2007.

In February 2007, five satellite groups of the Smithsonian mission were successfully launched. In March, the Northern Lights appeared over Alaska and Canada for two hours. At the same time, the satellite also detected the contact between charged particles and the North Pole magnetic field.

To Angelopoulos' surprise, the magnetic storm formed by the contact of charged particles with the magnetic field swept the air at a speed of 650 kilometers per minute, and its power was equivalent to an earthquake measuring 5.5 on the Richter scale.

Scientists have long suspected that the energy of the Northern Lights comes from the twisted magnetic field generated by the contact between charged particles and the Arctic magnetic field, but this theory was not confirmed until May 20 10, when the satellite group of the Semis mission first measured the structure of the twisted magnetic field from more than 60,000 kilometers above the earth.

Aurora is a large-scale discharge process around the earth. Charged particles from the sun arrive near the earth, and the earth's magnetic field forces some of them to concentrate along the magnetic field lines to the North and South poles.

The aurora observed in the northern hemisphere is called the Northern Lights, and the aurora observed in the southern hemisphere is called the Southern Lights. It often appears in two banded areas near 67 degrees north and south latitude. Fairbanks, Alaska has more than 200 days of aurora in a year, so it is called the "Northern Lights Capital".

The magnetic lines of the earth's magnetosphere bring the energy of the solar wind into the earth's interior, and then promote the formation of the geomagnetic field. In this closed loop of magnetospheric magnetic field lines, there are not only conductors inside the earth, but also weak conductors in the ionosphere in the atmosphere.

When the solar wind is strong, the magnetic flux energy meets the magnetic reactance inside the earth, and a lot of energy cannot be consumed, so the aurora is formed in the ionosphere.

Recently, because of the new satellite technology, Japanese scientists have directly observed the synthetic wave scattered electrons of charged particles deposited in the earth's atmosphere for the first time. The deposited electron current is strong enough to produce pulsating auroras.