Written by: Utsav Gautam - 23048, Grade XII
Posted on: 23 January, 2023
The northern lights, or the aurora borealis, are beautiful dancing waves of light
that have captivated people for millennia. But for all its beauty, this spectacular
light show is a rather violent event.The following image shows the phenomenon:
The northern lights are atmospheric phenomena that are regarded as the Holy
Grail of skywatching.
How does it happen?
Huge clouds of electrically charged particles are released by solar storms on the
surface of our star. Some of these particles may eventually collide with the Earth
after traveling millions of miles.
The majority of these particles are diverted, but some are caught in the magnetic
field of the Earth and these accelerate towards the north and south poles and into the
atmosphere. The magnetic poles are where aurora activity is concentrated because
of this.
Astronomer Tom Kerss of the Royal Observatory explains that when these
particles collide with atoms and molecules in the atmosphere of earth, they
effectively heat them up.
Difference in colours:
Different atoms found in the atmosphere of earth, such as oxygen and nitrogen are what give the Northern Lights their vibrant colours. At various atmospheric levels, these atoms are energized. Green is the Northern Lights' most frequent colour. When millions of oxygen atoms in the Earth’s atmosphere are simultaneously struck by the solar wind, the oxygen atoms are briefly excited before returning to their original state and emitting the green colour that is visible from the ground.
Oxygen atoms are also responsible for the occasional red light we see. These particles are high up in the atmosphere and are subject to a lower energy red light emission. The colour red is always there, but we don’t always see it because our eyes are five times less sensitive to red light than green.
Most of the earth's atmosphere is composed of nitrogen. Particles from the solar wind have to hit much harder to excite the nitrogen atoms. As nitrogen atoms begin to decompose, they emit violet lights. This is a rare colour and usually only occurs especially during active viewing.
Where does this happen?
When the electron solar wind reaches a planet, it first encounters the earth's magnetic field; this magnetic field deflects electrons. This deflection causes the electrons to move around the planet and strike near the polar regions where the magnetic field is the weakest. This is how daytime
auroras occur when electrons collide with the magnetic field facing the sun and are
deflected towards the poles.
But the solar wind doesn’t stop when it first hits the planet. It continues to move away from the sun to the other side of the earth, reaching the other side of our magnetic field; when they collide with the backside of the earth's magnetic field, the electrons are drawn towards the poles again, creating nighttime auroras.
