A solar wind is composed of ions of hydrogen, helium and it has other heavy elements. The heavy elements are Carbon, Nitrogen, and Oxygen. But don’t be fooled, just because their heavy elements doesn’t mean that they are slow they actually move at a speed of a million kilometers per hour!
Once the ions have a large enough amount of positive charge and collides with a comet, the electrons are pulled away from the neutral comet. This is called a charge exchange collision. The electrons that are captured in high-energy states of solar wind ions emit x-rays only when it shifts into lower energy states. If the x-rays is detected by the x-ray spectrometer it provides a signal that tells us that the change is happening.