So the solar wind is mostly electrons and protons with pretty high energy.
If these hit the spacecraft they can cause lots of effects. On the ground, we’re protected by our magnetic field.
The most obvious one I guess is on a manned mission – we need to make sure the astronauts don’t get a lethal dose of solar radiation. This isn’t too hard, we just shield the spacecraft. It might take the mass up a bit, but we can deal with that. The biggest problem in that case is solar flares, which are much worse.
However, the negative electrons and positive protons hitting the spacecraft can actually charge it up, just like rubbing your feet along a carpet to create static electricity. If that charge builds up it can eventually get so big it can create a spark (which is very easy in low pressure gases) that could fry some of the circuitry.
But the particles can also hit bits of the computer memory or processor, causing things called ‘latch up events’. The means that computer sometimes sees a 1 when it should be a 0 or the other way round. If lots of these happen then it can totally mess up the computer, which is bad for your spacecraft!
Because when you leave the Earth’s magnetic field you can get hit by the charged particles in the solar wind, and they would cause damage to the cells in your body. They also damage the electronics in space craft. So it’s just better to avoid them.
The solar wind can contain highly energised particles, that also cause the aurorae, and these can be harmful to us. In fact they are not dissimilar to radiation from nuclear reactors. They can also damage electronics, so both for us and for sensitive computers, in space there needs to be shielding.
The burning of the sun creates huge numbers of charged particles that come rushing out from the sun in all directions at speeds of nearly a million miles an hour! Although the particles are still small and spread out, there are enough to damage a rocket or your precious passengers.