Geomagnetic bays, their frequency and current‐systems

Birkeland see 1 of “References” at end of paper has made extensive studies of the field and current‐systems of bays, using data for magnetic stations of the Polar Year, 1882‐83, and less complete data for other years. In these important investigations he deduced considerable information respecting the geographical distribution of their fields and current‐systems. He suggested that the polar part of the current‐system in all probability flowed in (or beyond) the Earth's atmosphere with greatest concentration of current near the auroral zones at heights of 100‐700 km. Birkeland's supposition of an intake and outflow of current directly to or from the auroral zones has been shown to be somewhat doubtful and improbable as a consequence of later calculations of Vestine and Chapman 2. His findings, however, in the main have been confirmed, although notably extended and to some degree reshaped in later valuable discussions by Steiner 3, Wiechert 4, McNish 5, Chapman and Bartels 6 and Hatakeyama 7.