Introductory and Background Material - The Earth's Ionosphere: Plasma Physics and Electrodynamics - page 1

1 Introductory and Background

Material

In this introductory chapter we present a qualitative treatment of several topics that
we hope is sufficient to proceed with our study of ionospheric physics. The chapter
begins with historical comments and a description of the limitations we have set
for the text. In particular, we do not repeat or significantly update the material
published by Rishbeth and Garriott (1969) earlier in this same International Geo-
physics Series. Rather, our emphasis is on electrodynamics and plasma physics, so
we refer the interested reader to Rishbeth and Garriott and to Banks and Kockarts
(1973) for more information about formation of the ionosphere, its ion chemistry,
heat balance, and other aeronomic properties. Another and more recent resource
for classical ionospheric science is the text by Schunk and Nagy (2000). Lyons and
Williams (1984) have published a text on magnetospheric science.

1.1 Scope and Goals of the Text

1.1.1 Historical Perspective
The earth's ionosphere is a partially ionized gas that envelops the earth and in
some sense forms the interface between the atmosphere and space. Since the gas
is ionized, it cannot be fully described by the equations of neutral fluid dynamics.
In fact, a major revolution in ionospheric physics has occurred in the past decades
as the language and concepts of plasma physics have played an increasing role in
the discipline. On the other hand, the number density of the neutral gas exceeds
that of the ionospheric plasma, and certainly neutral particles cannot be ignored.
A student of the ionosphere must thus be familiar with both classical fluid dynam-
ics and plasma physics. Even a working knowledge of these two “pure” branches
of physics, however, is not sufficient. Since the ionosphere lies at the interface
between two very different and dynamic media, we must understand enough of
both atmospheric dynamics and deep space plasma physics to understand how
the ionosphere is formed and buffeted by sources from above and below. Added
to these two is the requirement for a sufficient knowledge of ion and neutral
chemistry and photochemistry to deal with production and loss processes.