Lowitz arc

A Lowitz arc is an optical phenomenon that occurs in the atmosphere; specifically, it is a rare type of ice crystal halo that forms a luminous arc which extends inwards from a sun dog (parhelion) and may continue above or below the sun.

History

The phenomenon is named after Johann Tobias Lowitz (or Lovits) (1757 - 1804), a German-born Russian apothecary and experimental chemist. On the morning of June 18, 1790 in St. Petersburg, Russia, Lowitz witnessed a spectacular display of solar halos. Among his observations, he noted arcs descending from the sun dogs and extending below the sun:

Original (in French): 6. Ces deux derniers parhélies qui se trouvoient à quelque distance des intersections du grand cercle horizontal par les deux couronnes qui entourent le soleil, renvoyoient d'abord des deux cotés de parties d'arc très courtes colorées xi & yk dont la direction s'inclinoit au dessous du soleil jusqu'aux deux demi-arcs de cercle intérieurs die & dke. En second lieu ils étoient pourvues des queues longues, claires & blanches x ζ & y η, opposées au soleil & renfermées dans la circonference du grand cercle afbg.

Translation : 6. These last two parhelia which were at some distance from the intersections of the great horizontal circle by the two coronas which surrounded the sun, sent, in the first place, from the two sides very short colored arcs xi & yk whose direction inclined below the sun as far as the two interior semicircular arcs die & dke. In the second place, they had long tails, bright and white x ζ & y η, directed away from the sun and included in the circumference of the great circle afhg.