The 46° Lowitz arcs and their history

The common halo observer in Central Europe will associate the term “Lowitz arcs” with short segments below the parhelic circle which connect the parhelia and the 22° halo. These so-called “lower Lowitz arcs” were first documented by T. Lowitz in St. Petersburg in 1790. In 1911, A. Wegener pointed out the hypothesis that these arcs might be caused by plate crystals oscillating around their equilibrium position. This statement is recorded in the classical textbook by J.M. Perter and F.M. Exner [1]. In contrast this, R. Greenler postulated that plate crystals might perform full 360° rotations as they fall, referring to a note from R.A.R. Tricker from 1972 [2]. Even today it is still under discussion which kind of crystal motion does occur in nature, since the Lowitz arc simulations for both assumptions coincide in their celestial position and differ only in their intensity distribution [3]. A couple of years after Greenler´s theoretical predictions, the middle and upper Lowitz arcs were observed and photographed in nature, e.g. 1985 in Knau, Thuringia, East Germany [4], 1988 in Dover, Delaware, USA [5] and 1994 in Vaala, Finland [6]. These observations were, however, not inspired by theory, as the arcs were identified only afterwards by comparison with the simulations. In the records of the German “Sektion Halobeobachtungen“ and the later “Arbeitskreis Meteore e.V.“, the upper Lowitz arc was categorized as “unknown halo“ or “abnormal Parry arc“. E. Tränkle presented a simulation of this arc independent from Greenler in 1995 [4].

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