Reflected Lowitz Arcs - Sweden

Last updated on September 16, 2023

Reflected Lowitz Arcs - A Fascinating Atmospheric Phenomenon in Sweden

Have you ever heard of Reflected Lowitz Arcs? These rare optical phenomena occur near Falköping, Sweden, and they are truly mesmerizing. In this article, we will delve into the captivating world of Reflected Lowitz Arcs, exploring their origins, characteristics, and the mysteries that still surround them.

Tobias Lowitz, a renowned scientist, first documented these arcs during the St. Petersburg display of 1790. However, it wasn't until the 1990s that they were captured in photographs, confirming their existence. Despite decades of research, there are still aspects of Reflected Lowitz Arcs that remain unexplained, adding to their enigmatic allure.

Traditionally, Lowitz arcs were described as faint curved arcs extending upwards and downwards from sundogs to the 22 degree halo. These arcs are formed by rays passing between inclined faces of Lowitz-oriented crystals. It is possible to observe up to three arcs - middle, upper, and lower - depending on the number of internal reflections within the crystals.

Interestingly, when the sun is low on the horizon, additional arcs appear. These arcs extend upwards from sundogs and outside the 22 degree halo, earning them the name "reflected" arcs. The term reflects their formation process, as rays undergo internal reflections from the large basal faces of the crystal plates. However, it is worth noting that a more suitable name is needed for these arcs, as there are numerous Lowitz arcs formed in this manner.

To distinguish between the different types of Reflected Lowitz Arcs, we could consider adopting a chemical nomenclature approach. For instance, we could use "gerade" (even) to represent arcs with an even number of internal reflections and "ungerade" (odd) for those with an odd number or no internal reflections. This naming convention would help categorize and differentiate the various components of Reflected Lowitz Arcs.

One remarkable aspect of Reflected Lowitz Arcs is their variability. The shape, intensity, and number of arcs can vary depending on atmospheric conditions and the properties of the crystal plates. The HaloSim simulation created by Lennart Ljuhs provides valuable insights into the formation of these arcs. By using very thin regular hexagonal plates with limited rotation about the Lowitz axis, Ljuhs was able to capture the upper "reflected" arcs with ray paths of 3, 1, 5. The simulation also suggests the presence of a weak middle arc, and possibly traces of lower and lower reflected arcs.

To improve the accuracy of the simulation, it is necessary to consider less regular hexagonal plates. This adjustment would better match the observed image and provide a more comprehensive understanding of Reflected Lowitz Arcs. The study of these atmospheric phenomena continues to evolve, with researchers striving to uncover the intricate details behind their formation.

In conclusion, Reflected Lowitz Arcs near Falköping, Sweden, offer a captivating spectacle for those fortunate enough to witness them. These optical wonders, first recorded by Tobias Lowitz in 1790, have sparked scientific curiosity for centuries. While many aspects of Reflected Lowitz Arcs remain unexplained, ongoing research and simulations like HaloSim contribute to our understanding of their formation and characteristics. As we delve deeper into the world of atmospheric optics, we uncover more of nature's hidden marvels, reminding us of the endless beauty that surrounds us.

Rare 'Reflected' Lowitz Arcs near Falk�ping, Sweden imaged on January 5, '09 by Lennart Ljuhs. The Lowitz arcs are the faint curved arcs extending upwards from each sundog and outside the 22 degree halo. There are traces of more Lowitz arcs to the right of the right-hand sundog. ©Lennart Ljuhs, shown with permission.

Tobias Lowitz first recorded the arcs that bear his name during the St. Petersburg display of 1790 but they remained elusive and their existence highly controversial until first photographed in the 1990s. Even now there remain aspects that are unexplained.

The traditional description of Lowitz arcs is of ones extending from sundogs upwards and downwards to the 22 degree halo. Up to three arcs, middle, upper and lower are possible from rays passing between faces inclined at 60 degrees to each other through Lowitz oriented crystals (usually plates, see the ray diagram at right).

However, when the sun is low, additional arcs form. Those above the horizon extend upwards from sundogs and outside the 22 degree halo. These are the so-called 'reflected' arcs because they are formed when rays undergo internal reflections from the large basal faces of the plates. A better name is needed because there are many Lowitz arcs formed in this manner and they are distinguished by whether the number of internal reflections is odd or even (or zero) and whether they are middle (M), upper (U) or lower (L)ray paths. Lowitz was a professor of chemistry at St. Petersburg and we could perhaps honour him by following chemical nomenclature and name the components g = gerade for even reflections and u = ungerade for odd.

The HaloSim simulation of Lennart Ljuh's display (at right) is preliminary. Rays from Lowitz oriented crystals appear in red. Very thin regular hexagonal plates with limited rotation about the Lowitz axis (AA) were used. Ljuh's strong arcs are upper 'reflected' arcs with ray paths of 3,1,5. Strong enhancement shows a weak middle arc (M). There are also possibly traces on the right hand side of the lower (L) and lower reflected arc (LR). An improved match with the image might be obtained from less regular hexagonal plates.

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