Q15. What are aurora australis and aurora borealis? How are these triggered? (15M)

Introduction

Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights) are natural light displays in the sky, predominantly seen in high-latitude regions around the Arctic and Antarctic. These phenomena are caused by the interaction between the Earth’s magnetic field and charged particles from the Sun. The auroras appear as glowing curtains of light, often green, pink, red, yellow, or violet, and are most visible during clear, dark nights.

Aurora Borealis and Aurora Australis:

• Aurora Borealis:

• Also called the Northern Lights, it occurs in the Northern Hemisphere, near the Arctic regions. Countries such as Norway, Sweden, Finland, Canada, and Alaska are prime locations to witness the aurora borealis.

• Also called the Northern Lights, it occurs in the Northern Hemisphere, near the Arctic regions.

• Countries such as Norway, Sweden, Finland, Canada, and Alaska are prime locations to witness the aurora borealis.

• Aurora Australis:

• Also called the Southern Lights, it occurs in the Southern Hemisphere, near the Antarctic region. The aurora australis is primarily visible from Antarctica, southern parts of New Zealand, and Australia.

• Also called the Southern Lights, it occurs in the Southern Hemisphere, near the Antarctic region.

• The aurora australis is primarily visible from Antarctica, southern parts of New Zealand, and Australia.

Both phenomena are essentially the same in terms of their cause and behaviour, with the only difference being their location.

#### The triggering of Aurora:

• Solar Wind: Auroras are triggered by solar wind, a stream of charged particles (mainly electrons and protons) emitted by the Sun. These particles travel through space and can reach Earth when solar activity, such as solar flares or coronal mass ejections (CMEs), increases.

• Interaction with Earth’s Magnetic Field: When these charged particles reach Earth, they are guided by the Earth’s magnetic field toward the polar regions. The Earth’s magnetic field funnels the particles toward the poles, which is why auroras are more frequent near the Arctic and Antarctic circles.

• Excitation of Atmospheric Particles: As the charged particles from the solar wind collide with atoms and molecules in the Earth’s atmosphere (mainly oxygen and nitrogen), they transfer energy to these particles. This process is called excitation, where electrons in the atoms absorb energy and jump to a higher energy state.

• This process is called excitation, where electrons in the atoms absorb energy and jump to a higher energy state.

• Emission of Light: When the excited atoms return to their normal state, they release the absorbed energy in the form of light. The colour of the aurora depends on the type of gas involved in the collision and the altitude at which the interaction occurs: Oxygen at higher altitudes (about 150-300 km) produces a green or red Nitrogen at lower altitudes (up to 100 km) produces blue or purplish

• Oxygen at higher altitudes (about 150-300 km) produces a green or red

• Nitrogen at lower altitudes (up to 100 km) produces blue or purplish

• Geomagnetic Storms: When there is a particularly strong solar storm, the influx of charged particles increases, leading to more intense auroras, visible even in lower latitudes.

Key Factors Influencing Aurora Intensity:

• Solar activity cycles (approximately 11-year cycles)

• Geomagnetic storms

• Season and time of day (more visible during darker months)

• Latitude (more common closer to the magnetic poles)

Conclusion

Auroras are one of nature’s most spectacular displays, resulting from the interaction between the Earth’s magnetic field and solar particles. These phenomena not only provide stunning visual displays but also offer insight into the relationship between solar activity and the Earth’s magnetosphere.