Aurora Lights | Geomagnetic Solar Storms

Context (IE | NDTV): The Aurora lights were not visible in most parts of India recently, but Indian ground stations have observed the solar flares that caused them.

Aurora Lights or Northern Lights

Aurora results when the charged particles from the Sun collide with gases in Earth’s upper atmosphere.
During a geomagnetic storm, magnetic fields break, allowing particles to reach the upper atmosphere.

Different gases give off different colours when they are heated.
Two primary gases in the Earth’s atmosphere: nitrogen and oxygen.
When Charged particles from the sun collide with,
- Oxygen atoms they emit green and red light.
- Nitrogen molecules emit blue and purple light.

The boundary between the solar wind and Earth’s magnetic field is called the magnetopause.
Any planet with an atmosphere and magnetic field is likely to have aurorae.
Auroras occur within one of Earth’s upper atmosphere layers, the thermosphere.

Geomagnetic storms are disturbances in the Earth’s magnetic field.
Caused by the interaction between the solar wind and the planet’s magnetosphere.
Geomagnetic storms typically originate from the Sun. They are caused by two main phenomena:
- Coronal Mass Ejections (CMEs): Massive bursts of plasma and magnetic fields ejected from the Sun’s surface.
- Solar Flares: Intense eruptions of electromagnetic radiation from the Sun’s surface.
These storms can have significant impacts on technology, infrastructure, and even human health.

Solar flares are categorised based on strength: B-class is the smallest, followed by C, M, and X-class, which are a thousand times stronger than B-class flares.
Solar flares are typically more frequent during the solar maximum.
Solar cycle is the cycle that the Sun’s magnetic field goes through approximately every 11 years.
- Solar minimum is when the Sun has the least sunspots.
- Solar maximum is when the Sun has the most sunspots.

A magnetosphere is the region around a planet dominated by the planet’s magnetic field.
It is generated by the convective motion of charged, molten iron in Earth’s outer core.
Significance: It traps high-energy radiation particles and shields the Earth from solar storms.
These trapped particles form two belts of radiation, known as the Van Allen Belts.
- Outer belt is made up of billions of high-energy particles that originate from the Sun.
- Inner belt results from interactions of cosmic rays with Earth’s atmosphere.
Astronauts must fly through the Van Allen Belts to reach outer space, so it is important to fly through this region quickly to limit their exposure to radiation.