Places we find refreshing such as in the mountains and near waterfalls and seashores - where health resorts are traditionally situated - are found to have high concentrations of negative ions. But areas with high levels of positive ions often make us feel uncomfortable and irritable.

Many people find the atmosphere before a storm is 'heavy' and oppressive. This has been attributed to the high levels of positive ions that build up in the air, which are also believed to be the trigger of "storm-sensitivity" in asthmatics and many other  people. Certainly, in laboratory conditions, similar symptoms could be triggered in subjects when they were exposed to abnormally high levels of positive ions.

In the hours before this storm arrived, hundreds of people  reported to hospitals with severe asthma attacks. Was it due to positive ions?

In the upper atmosphere the action of the Sun's ultra violet rays, forms a thick band of ions called the ionosphere, which starts at 60 kilometers, and finishes around 100 kilometers, above the Earth. It is the ionosphere that reflects radio waves back to earth, allowing us to broadcast over long distances. The reason distant stations fade after dark is because the ions diminish as the sunlight disappears.
 

The Sun is constantly ejecting streams of charged particles into space. (This is known as the solar wind). As these particles approach the Earth they are caught in its magnetic field and swept round to the North and South poles. Pouring into the atmosphere, they ionize its component gases in a spectacular display of glowing colors, called the Aurora.