Auroral green line

Abstract

I note with interest the paper (Eos, July 19, 1988) by Hendriksen and Egeland [1988] concerning the beginning of auroral spectroscopic research. I am writing this note to call attention to early work on auroral spectroscopy that was not mentioned in their paper.The background to the development of auroral spectroscopy was provided by the new academic disciplines of astrophysics and electron physics. First, I call attention to the work of Karl Friedrich Zöllner (1834–1882), who became, in the 19th century, the first professor of astrophysics at the University of Leipzig. Zöllner worked mainly in the field of photometry. He developed new instruments for spectral investigations of solar flares. He was interested in solar‐terrestrial relationships, and he observed the auroral green line. During the great aurora of October 25, 1870, he observed both green and red auroral lines. He interpreted his observations as a consequence of impact on Earth's atmosphere by solar particles [Zöllner, 1881]. In the paper entitled “Uber den Ursprung des Erdmagnetismus und die magnetischen Beziehungen der Weltkorper” (1871, reprinted in the work of Zöllner [1881]) he dealt with several physical aspects of solar‐terrestrial relationships, as well as the nature of the aurora borealis. He suggested that solar activity has an impact on magnetic variations. From measurements of the auroral green line, Zöllner and later, K. H. Vogel (1842–1907) [cf. Vogel, 1872] concluded that auroras are caused by solar particles impacting the upper atmosphere (see also Schröder [1984]).