Remote sensing of the upper atmosphere by VLF

The part of the electromagnetic spectrum described as VLF (Very Low Frequency) generally spans 3-30 kHz (Kraus, 1984). In this chapter we will concentrate on observations made using strong VLF radiation to better understand the natural sources, such as lightning, and as long-range probes into the electrical properties of the upper atmosphere. However, in doing this we are restricting ourselves to a small subsection of VLF studies; the interested reader is directed to a recent and broad review article (Barr et al., 2000) for a wider description of studies involving VLF radio waves, and to the material of other contributors in this book.