In this short tutorial we first briefly review the basic physics ofthe E-region of the equatorial ionosphere, with emphasis on thestrong electrojet current system that drives plasma instabilitiesand generates strong plasma waves that are easily detected by radarsand rocket probes. We then discuss the instabilities themselves,both the theory and some examples of the observational data. Theseinstabilities have now been studied for about half a century (!),beginning with the IGY, particularly at the Jicamarca RadioObservatory in Peru. The linear fluid theory of the importantprocesses is now well understood, but there are still questionsabout some kinetic effects, not to mention the considerable amountof work to be done before we have a full quantitative understandingof the limiting nonlinear processes that determine the details ofwhat we actually observe. As our observational techniques,especially the radar techniques, improve, we find some answers, butalso more and more questions. One difficulty with studying naturalphenomena, such as these instabilities, is that we cannot performactive cause-and-effect experiments; we are limited to the inputsand responses that nature provides. The one hope here is thesteadily growing capability of numerical plasma simulations. If wecan accurately simulate the relevant plasma physics, we can controlthe inputs and measure the responses in great detail. Unfortunately,the problem is inherently three-dimensional, and we still needsomewhat more computer power than is currently available, althoughwe have come a long way.
展开▼
