How can solar wind affect astronauts?
They are so deadly that they can kill an astronaut!
That which is referred to as "solar wind" is the sun ejecting various forms of radiation in varying amounts, x-rays, gamma-rays, infrared, ultraviolet and visible light. These emissions are constant but under normal conditions, astronauts are well-protected from them in both the space craft and their space suits, although the latter is subject to time restrictions as no protection is perfect.
The most dangerous time is during a CME (corona mass ejection) when the sun suddenly shoots out a massive amount of radiation. Astronauts must be in their space craft during such periods as outside exposure would likely be deadly.