Every second, 1 million tonnes of matter is blasted from the surface of the Sun, which travel at the velocity of a stupendous 1 million miles per hour. These matters travel in every direction and also Earth. At such a velocity, this army of matter is on a mission to collide our planet Earth. But this is not something we need to worry about, because this give rise to one of the most beautiful phenomenons of planet Earth- the Northern Lights, also called as the Auroras.
These lights are formed at the Northern and the Southern poles and named as Aurora Borealis and Aurora Australis respectively. These are formed when the army of high-energy particles collide with the neutral atoms of the Earth's atmosphere. This collision brings to life a picturesque phenomenon, which mankind has marveled at for centuries.
Let us learn this concept in three phases-
1. Energy emitted from sun
The pressure on the sun is so enormous, that the hydrogen atoms start combining to form Helium atoms. The energy in form of heat thus released in this process is radiated outward in form of huge arrays called the convection cells. These electrical currents of charged cells create magnetic field inside the sun. Sometimes this magnetic field push themselves out of the surface of the sun and they slow down the flow of the hot gas at those points, causing a cool down resulting in dark spots on the surface of the sun.
This electrically charged gas is called as plasma. Plasma drags the magnetic field further outwards. The magnetic field then stretches and bends like a rubber band. The rubber band then breaks and millions of tonnes of plasma is hurled out of the sun. This is called the solar storm. The speed of this solar storm is so magnificent that it takes only 18 hours to reach the Earth.
2. A hindrance at the Earth's magnetic field
When the solar storm reaches the Earth, an invisible magnetic field deflects the solar storm. The outer surface of the Earth's magnetic field breaks down and are pushed backward to the other side of the Earth where they are coupled together. The high energy gas then goes through the line of the magnetic field and reaches the daylight side of the poles. This magnetic field couple again at the other side of the Earth, couple together and break down like a twisted rubber band. This will bring down the high energy gas along the lines of the magnetic field to the night-time pole of the Earth. These arrivals of high energy gas at the day-time and night-time poles cause Aurora Borealis and Aurora Australis respectively.
3. Colour of the Aurora
The sun radiates all visible colors, which is why sunlight appears white. The spectrum of visible light associated with the aurora is much more restricted. The aurora is caused by charged particles in the solar wind colliding with atmospheric atoms and ions. The collisions cause the electrons of the atmospheric atoms to become excited. As the electrons return to their original energy levels, these atoms emit visible light of distinct wavelengths, to create the colors of the display we see.
The color of the aurora depends on the wavelength of the light emitted. This is determined by the specific atmospheric gas and its electrical state, and the energy of the particle that hits the atmospheric gas. The atmosphere consists mainly of nitrogen and oxygen, which emit the characteristic colors of their respective line spectra. Atomic oxygen is responsible for the two main colors of green (wavelength of 557.7 nm) and red (630.0 nm). Nitrogen causes blue and deep red hues.
Most of the auroral features are greenish-yellow, but sometimes the
tall rays will turn red at their tops and along their lower edges. On
rare occasions, sunlight will hit the top part of the auroral rays to
create a faint blue color. On very rare occasions (once every 10 years
or so) the aurora can be a deep blood red color from top to bottom. Pink
hues may also be seen in the lower area of the aurora. In addition to
producing light, the energetic auroral collisions transmit heat. The
heat is dissipated by infrared radiation, or transported away by strong
winds in the upper atmosphere.
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These lights are formed at the Northern and the Southern poles and named as Aurora Borealis and Aurora Australis respectively. These are formed when the army of high-energy particles collide with the neutral atoms of the Earth's atmosphere. This collision brings to life a picturesque phenomenon, which mankind has marveled at for centuries.
Let us learn this concept in three phases-
1. Energy emitted from sun
The pressure on the sun is so enormous, that the hydrogen atoms start combining to form Helium atoms. The energy in form of heat thus released in this process is radiated outward in form of huge arrays called the convection cells. These electrical currents of charged cells create magnetic field inside the sun. Sometimes this magnetic field push themselves out of the surface of the sun and they slow down the flow of the hot gas at those points, causing a cool down resulting in dark spots on the surface of the sun.
This electrically charged gas is called as plasma. Plasma drags the magnetic field further outwards. The magnetic field then stretches and bends like a rubber band. The rubber band then breaks and millions of tonnes of plasma is hurled out of the sun. This is called the solar storm. The speed of this solar storm is so magnificent that it takes only 18 hours to reach the Earth.
2. A hindrance at the Earth's magnetic field
When the solar storm reaches the Earth, an invisible magnetic field deflects the solar storm. The outer surface of the Earth's magnetic field breaks down and are pushed backward to the other side of the Earth where they are coupled together. The high energy gas then goes through the line of the magnetic field and reaches the daylight side of the poles. This magnetic field couple again at the other side of the Earth, couple together and break down like a twisted rubber band. This will bring down the high energy gas along the lines of the magnetic field to the night-time pole of the Earth. These arrivals of high energy gas at the day-time and night-time poles cause Aurora Borealis and Aurora Australis respectively.
3. Colour of the Aurora
The sun radiates all visible colors, which is why sunlight appears white. The spectrum of visible light associated with the aurora is much more restricted. The aurora is caused by charged particles in the solar wind colliding with atmospheric atoms and ions. The collisions cause the electrons of the atmospheric atoms to become excited. As the electrons return to their original energy levels, these atoms emit visible light of distinct wavelengths, to create the colors of the display we see.
The color of the aurora depends on the wavelength of the light emitted. This is determined by the specific atmospheric gas and its electrical state, and the energy of the particle that hits the atmospheric gas. The atmosphere consists mainly of nitrogen and oxygen, which emit the characteristic colors of their respective line spectra. Atomic oxygen is responsible for the two main colors of green (wavelength of 557.7 nm) and red (630.0 nm). Nitrogen causes blue and deep red hues.
This is the spectrum of colors emitted by the various atoms in earth’s outer atmosphere.
