What's a solar storm made up of?

Katie asked this physics question, so we put it to Chris Rogers...

Chris R - A solar storm is a really interesting phenomenon. It's to do with space weather. What we see on Earth is, we see the magnetic field of the Earth actually changes, and we see a really fantastic light display with the aurora, and what's going on is charged particles are flying from the Sun towards the Earth and bashing into the Earth. You get this charged plasma and that actually physically changes the Earth's magnetic field.

Phil - What are those particles?

Chris R - Typically they're protons, or ions, or electrons. So the Sun is mostly made up of hydrogen with a bit of helium mixed in. And so typically you're getting ions from that hydrogen, helium, and electrons associated with those ions.

Phil - What are the effects of this? When you've got all these particles bashing into the Earth and its atmosphere?

Chris R - So if it's a small solar storm, then you see a really bright Aurora. So the whole sky lights up in the far North. With a really bright solar storm, you can get amazing effects. So there's a famous event in the 19th century called the Carrington Event, where just at the beginning of the invention of electricity, they had telegraph wires. The telegraph wires, would actually spark out. You'd get these really big sparks coming from the telegraph wires.

Chris S - Can the Earth gain mass that way? And the reason for asking you, Chris, is that Steve Rampley, has just pinged us an email and said, "is the mass of the Earth changing? Is one way that the Earth's mass can change from particles coming in from outer space?"

Chris R - That's an interesting question. I don't know whether the Earth's mass can change, but I do know that the Sun's mass can change. So the Sun is slowly losing mass as it fires off all of these high energy particles, those particles are flying out into the intergalactic medium and so the Sun itself is losing mass.

Chris S - Is it not also losing mass because it's sending energy to us in the form of light? And that light must have come from a process that consumed mass in the Sun in order to produce the energy that it radiated at us in the first place. So that would also lose mass for that reason.

Chris R - That's a really good point. So of course Einstein tells us again, Einstein again, that clever guy, he tells us that mass and energy are interchangeable. So when hydrogen fusion happens, hydrogen fuses into helium and the mass of the helium is lower than the mass of the hydrogen.