Shedding light on what happens on the face of the sun

The effects of solar flares can be far-reaching. Picture: Shutterstock
The effects of solar flares can be far-reaching. Picture: Shutterstock

The sun is taken as a constant in our lives - it has been there for billions of years, and will be for billions to come - but do you ever think about what's happening on the sun, right now?

Although the sun looks quiet from Earth, sometimes there's a lot happening on its surface. This is called solar activity and mostly refers to sunspots and flares.

The sun has an activity cycle, called the "solar cycle". This means that sometimes it is more active and at other times it is quiet - almost like it goes into hibernation.

The sun doesn't get any dimmer or colder during its quiet time, there just isn't as much happening at the surface. In fact, we are coming out of one of the sun's quiet times right now.

The solar cycle lasts about 11 years, meaning there are about 11 years between each quiet time and 11 years between the most active times.

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At an active time, the sun has lots of sunspots, solar flares and other events occurring, and all these events are related - they are even related to the aurora we sometimes see on Earth.

The sun has a very strong magnetic field, which you can imagine as a giant sun-sized magnet with a north and a south pole. The sun's magnetic field flips (north and south swap) every 11 years - at roughly the same time as the sun's quiet times - driving the solar activity we see.

The equator of the sun rotates faster than its poles which means magnetic fields get all wound up and tangled - think of pulling a piece of string from the middle instead of each end.

Sometimes when the magnetic fields are tangled, they break apart and make new magnetic loops - which you can think of as smaller magnets. The feet of these loops are what we see as sunspots. The middle of a sunspot is slightly colder than the rest of the sun, making it look darker.

An image of the sun from 2014 taken with NASAs Solar Dynamics Observatory. Picture: NASA/SDA

An image of the sun from 2014 taken with NASAs Solar Dynamics Observatory. Picture: NASA/SDA

Sunspots are also the place where solar flares start. Charged particles spin around magnetic field loops at great speeds, and when these loops break, the particles get flung out into space. The charged particles being thrown into space are called a solar flare, and sometimes the particles can make it Earth and create the aurora in our atmosphere at the north and south poles.

It's not just the planets in the Solar System that feel the effects of a big solar flare - the sun can feel them too ... some of the energy in the flare gets sent back into the sun, causing what is known as a solar quake.

It's not just the planets in the Solar System that feel the effects of a big solar flare - the sun can feel them too. Sometimes instead of going out into space, some of the energy in the flare gets sent back into the sun, causing what is known as a solar quake.

Astronomers can use these quakes in the same way that earthquakes are used to understand the structure of the Earth; using the time of the impact and the time it takes for a quake to start can teach us about some of the internal layers of the Sun.

So the next time you admire a lovely sunset or have a sunny day, think about all the interesting things happening on the sun that we don't see.

  • Eloise Birchall has a Masters of Astronomy and Astrophysics (Advanced) from the Research School of Astronomy and Astrophysics at the Australian National University.
This story Shedding light on what happens on the face of the sun first appeared on The Examiner.