Radiation is a common word, but in space weather studies, there are two types that differ in important ways.

Matter - in the form of electrons, protons and the ions of various atoms, which travel much slower than the speed of light.

Electromagnetic - In the form of X-rays, visible light, gamma rays and other forms of energy that travel at the speed of light.



Radiation: most of us have an instinctive fear of it. Even the word, itself, is cloaked in mystery and a sense of foreboding. In reality, we are all more familiar with radiation than we suspect. No matter where you live, you receive 15-20 chest X-rays each year of environmental radiation - and there is almost nothing you can do about it. Even solar storms add their share to this cargo of potential damage. The figure above is from the World Nuclear Association


As you sit reading this page, you are being pummeled by various forms of electromagnetic energy from visible light to radio waves. You are also being struck by the daughters of particles that have streamed, literally, from the far corners of our universe. In casual conversation, these kinds of energy are simply called 'radiation' even though physicists have known for over a century that their various forms are quite different. Electromagnetic radiation includes the familiar rainbow of the visible spectrum, crammed between a vast range of other waves traveling at the speed of light. Some of these can be stopped by a sheet of ordinary paper. Other more energetic forms of light, like X-rays and gamma rays, require ever increasing thicknesses of matter to abate them.
In a separate category of radiation we have fast-moving particles which also come in several basic types such as electrons, protons, and the nuclei of the elements heavier than hydrogen. The amount of damage that these material forms of radiation can inflict depends on how much energy each particle is carrying. The bigger the energy, the more punch they can deliver, and the more collateral damage they produce as they penetrate the skin of a spacecraft, or the tissues in an organism. Electromagnetic radiation in the ultraviolet can give you a sunburn, but energetic particles can bore their way into your cells and explode like a small bomb, 'nuking' a gene.


Read more http://www.solarstorms.org/Sradiation.html