An ion is formed when an atom loses one or more electrons. This happens when the temperature gets high and the gas particles start bashing and crashing into each other. The high temperature of the solar atmosphere means that atoms lose lots of electrons.

The iron (Fe) atom has 26 electrons, but in the corona the temperature is so hot, over one million degrees, that it usually only has between 13 and 18 electrons left. An iron ion with 13 electrons stripped off is called Fe+13, since it now has a positive charge of +13.

Did you know? A familiar example of how the properties of atoms change when you remove electrons is provided by salt. Salt is made from sodium and chlorine - two of the nastiest elements in your chemistry lab! Chlorine is a poisonous gas, whereas sodium is a metal which can burn you. When they are brought together, however, sodium gives an electron to chlorine and makes harmless salt.