In the early 1950s, space near Earth was thought to be mostly empty. Radio waves produced by lightening held the clues that would eventually change that, but it took more than 10 years and tough times for young researchers to correct the prevailing view. Another forty years later our understanding changed again when point-by-point measurements by orbiting spacecraft wereaugmented by visual images of ionized helium gas surrounding Earth. Primarily composed of cold ionized hydrogen, this envelop of relatively dense plasma originating in the ionosphere is called the plasmasphere. How we came to know of it, its properties, its dynamics, and how we have finally seen it will be discussed.
