Introduction

Abstract

The ionosphere is a part of the earth’s upper atmosphere, extending in height from 60 to about 1000 km. In this region, the atmosphere is a partly ionized gas or plasma. The processes that occur in the ionospheric plasma are closely connected with the wave and corpuscular radiation of the sun, with events in the magnetosphere and variation of the earth’s magnetic field, with motion of the upper atmosphere, and so on. This is why the ionosphere varies so greatly with time (with the time of day, with the season of the year, with the 11-year cycle of solar activity) and with geographic latitude.