Geoscience Reference
In-Depth Information
space to start from the first principles of ionospheric science, particularly with
regard to photoproduction, ion chemistry, recombination, and related topics. In
this first chapter, we attempt a broad general introduction to this area, which
we hope will provide enough background to make the remainder of the text
meaningful.
It is also necessary to introduce elements of neutral atmospheric and mag-
netospheric physics, since the ionosphere is very much affected by processes
that originate in these two regions. The ionosphere coexists with the upper por-
tion of the neutral atmosphere and receives considerable energy and momen-
tum from the lower atmosphere as well as from the magnetosphere. The energy
and momentum fluxes are carried by particles, electromagnetic fields, and atmo-
spheric waves. We devote some time in this first chapter to a qualitative descrip-
tion of the atmosphere and magnetosphere. Although useful as a starting point,
the descriptive approach is not sufficient in all aspects, and we will treat some
particularly important processes, such as gravity waves, in detail as they arise in
the text.
Some knowledge about experimental techniques is necessary for a student of
ionospheric dynamics, if only to understand the sources of the data. Accordingly,
Appendix A is included, describing some of the most important measurement
methods. The choice of instruments so dealt with is not exhaustive and certainly
reflects the bias and expertise of the author.
Finally, we need to limit the scope of the text. We have somewhat regret-
fully chosen not to include a detailed discussion of the acceleration of auro-
ral particle beams. Part of the rationale for this decision concerns the height
range where the electron acceleration usually takes place, some 2000 km or
more above the earth's surface, which is the limiting height range of the iono-
sphere as we define it here. Thus, even though particle acceleration can and does
occur much lower than the 2000 km height, we consider this topic to be outside
the domain of this topic, if not always outside the height range under detailed
consideration.
In Chapter 2 some basic equations and concepts are developed for use through-
out the text. Some of these concepts would be quite useful as background for
reading the rest of this first chapter, particularly the magnetospheric section. We
thus recommend that a reader unfamiliar with the field read Chapter 1 twice,
once for background and once again after reading Chapter 2. Chapters 3 and
4 deal with the electrodynamics and plasma physics of the equatorial iono-
sphere. This region is singled out, since the earth's horizontal magnetic field
in that area leads to a number of unique phenomena. An interesting analogy
exists with atmospheric and ocean dynamics. Since the Coriolis force vanishes
at the equator, there are some unique phenomena common to both meteorology
and oceanography that make equatorial dynamics very unusual and interesting.
Chapters 5 and 6 deal with the tropical and midlatitude ionosphere, where the
earth's magnetic field has a sizable inclination but is not vertical and usually
does not link the ionosphere with the hot, tenuous, flowing plasmas of the
Search WWH ::
Custom Search