An important feature of the upper atmosphere is its ability to conduct electricity through the movement of negative ions, which are whole or part-molecules to which electrons have become attached. Electrons are the negatively charged parts of an atom. They are stripped from normal atoms of the air's gases in the course of bombardment by cosmic radiation, which consists of high-energy atomic nuclei from outer space, along with the products of their collisions with air molecules. In other words, the electron-stripping process in the upper atmosphere results in ionisation (Figure 1.4). The process absorbs cosmic radiation, and thereby protects us from it.
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