This book presents a detailed account of polar radio science and geomagnetic research conducted throughout the International Years of the Quiet Sun (IQSY). This pivotal scientific period, spanning January 1, 1964, to December 31, 1965, near solar minimum, marked an international effort to observe solar and geophysical phenomena using both ground‑based observatories and spacecraft, with the intention to deepen a global understanding of solar—terrestrial interactions—particularly how disturbances originating from the Sun influence Earth’s upper atmosphere, ionosphere, and magnetic environment. The work followed an earlier global campaign, the International Geophysical Year (IGY) of 1957–1958, which focused on measurements taken under conditions of an active Sun. Together, these two major scientific initiatives sought to compare and understand the differences between solar maximum and solar minimum conditions. Much of the resulting data came from optical instruments and specially designed upper‑atmospheric radio receivers used to probe the ionosphere, especially during polar cap absorption (PCA) events and auroral absorption (AA) phenomena.

The purpose of this book is to explore these two hemispheric research efforts in depth, revealing the scientific experiments, measurement methods, and field experiences that shaped them.