Astronomy Telescopes

Climate explained: How particles ejected from the sun affect Earth's climate

This article was originally published at The Conversation. The publication contributed the article to Space.com’s Expert Voices: Op-Ed & Insights.

Annika Seppälä, Senior Lecturer in Geophysics, University of Otago

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

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When the Sun ejects solar particles into space, how does this affect the Earth and climate? Are clouds affected by these particles?

When we consider the sun’s influence on Earth and our climate, we tend to think about solar radiation. We are acutely aware of the skin-burning dangers of ultraviolet, or UV, radiation.

But the sun is an active star. It also continuously releases what is known as “solar wind,” made up of charged particles, largely protons and electrons, that travel at speeds of hundreds of kilometres per hour.

Some of these particles that reach Earth are guided into the polar atmosphere by our magnetic field. As a result, we can see the southern lights, aurora australis, in the southern hemisphere, and the northern equivalent, aurora borealis.

The southern lights, less-photographed than their northern counterparts, are seen from the air in a recent charter flight from New Zealand. (Image credit: Stephen Voss/YouTube)

This visible manifestation of solar particles entering Earth’s atmosphere is a constant reminder there is more to the sun than sunlight. But the particles have other effects as well.

Read more: Why is the sun’s atmosphere so hot? Spacecraft starts to unravel our star’s mysteries

Solar particles and ozone

When solar particles enter the atmosphere, their high energies ionise neutral atmospheric nitrogen and oxygen molecules, which make up 99% of the atmosphere. This “energetic particle precipitation,” named because it’s like a rain of particles from space, is a major source of ionisation in the polar atmosphere above 30 km

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