Appropriating the Aurora: Christopher Hansteen and the Circumpolar Auroral Rings

Abstract

The Norwegian astronomer and mathematician Christopher Hansteen (1784–1873) is best known for his career-long contribution to the study of terrestrial magnetism. In his monumental Magnetismus der Erde (1819), he suggests that the earth had two magnetic axes and thus four magnetic poles. It is less known that Hansteen planned to publish a second part of Magnetismus der Erde devoted solely to the polar lights, but this work was never completed. In this article, I reconstruct Hansteen's strategy for studying the aurora borealis and explain how the polar lights were connected to his four-pole theory. I emphasize in particular the spatial and geographical dimension of Hansteen's approach, focusing on his analysis of both the auroral corona and the auroral ring. In accordance with his own theory of terrestrial magnetism, he suggested the existence of four such circumpolar auroral rings, each centered around one of the four magnetic poles identified in Magnetismus der Erde. Hansteen's auroral project entailed an appropriation of earlier ideas and methods, especially those of Edmond Halley and Alexander von Humboldt. He sought to bolster the claim for the privileged position of the Scandinavian countries for observing and analyzing the aurora.