***Picture of Sun blowing***

There is a constant stream of gas coming from the Sun. We call this the solar wind because its a bit like wind that blows on Earth, except it's in space! CMEs of course add a reasonable amount of material to the solar wind and they get carried along by it. Studying how many CMEs there are and where they happen helps us to decide just how much gas CMEs add to the solar wind.

No, the total amount of gas in the solar wind is small compared to the mass of the Sun. Even a large CME is only a tiny, tiny fraction of the Sun's mass. In fact if the loss of mass like this was the only way the Sun changed with time, it would last about 300,000,000,000,000 years!!

HOW DO CMES HAPPEN?

We are still not fully sure how CMEs happen but we do know that the Sun's magnetic field plays a major role.

The Sun like the Earth has a magnetic north and south pole, again a bit like a bar magnet. There are lots of magnetic lines which go from north to south. These get pushed up into the corona and form giant arches.

*** LASCO IMAGE SHOWING ARCH IN C1 ***

As the surface of the Sun moves about these magnetic lines get tangled and twisted. This stretches them like elastic bands and just like elastic bands they can snap. This releases a lot of magnetic energy and heat and a CME is born.

Sometimes CMEs are not alone. Solar flares, which are sudden brightenings of small portions of the Sun can accompany CMEs and some CMEs are followed by the eruption of huge arcs of gas called prominences.

*** EIT PROMINENCE MOVIE ***

This is a huge arc of material low down in the corona that blows out after a CME has happened. It is hundreds of times larger than the Earth!

WHAT HAS LASCO TOLD US ABOUT CMES?

Since CMEs are so large and happen so often we must understand them if we want to know how the Sun works. It's like the Sun keeps coughing and we want to know what's making it ill!

LASCO has helped us to understand CMEs better. We now know that,

They happen more often that we expected -- about one a day during solar minimum and more than this during solar maximum.

*** LASCO IMAGE OR MOVIE SHOWING MULTIPLE CMES ***

Some of them are larger than we expected as well.

We can see more CMEs with LASCO and we can watch them as they move far into space and because LASCO watches the Sun nearly all the time it gives us warnings of when solar storms are going to hit the Earth.