An Optical Atmospheric Phenomenon Observed in 1670 over the City of Astrakhan Was not a Mid-Latitude Aurora

TL;DR

This study reanalyzes a 1670 astronomical event over Astrakhan, demonstrating it was a sundog, not a mid-latitude aurora, thus challenging previous claims of a severe geomagnetic storm during the Maunder minimum.

Contribution

The paper corrects a misinterpretation of historical records, clarifying that the 1670 event was a solar halo, not an aurora, impacting understanding of geomagnetic activity in the Maunder minimum.

Findings

The 1670 event was a sundog, not an aurora.

Historical record analysis corrected previous misinterpretation.

No evidence of a severe geomagnetic storm in 1670.

Abstract

It has been recently claimed (Zolotova and Ponyavin, Solar Phys., 291, 2869, 2016, ZP16 henceforth) that a mid-latitude optical phenomenon, which took place over the city of Astrakhan in July 1670, according to Russian chronicles, was a strong aurora borealis. If this was true, it would imply a very strong or even severe geomagnetic storm during the quietest part of the Maunder minimum. However, as we argue in this article, this conclusion is erroneous and caused by a misinterpretation of the chronicle record. As a result of a thorough analysis of the chronicle text, we show that the described phenomenon occurred during the daylight period of the day ("the last morning hour"), in the south direction ("towards noon"), and its description does not match that of an aurora. The date of the event was also incorrectly interpreted. We conclude that this phenomenon was not a mid-latitude aurora but an atmospheric phenomenon, the so-called sundog (or parhelion) which is a particular type of solar halo. Accordingly, the claim about a strong mid-latitude aurora during the deep Maunder minimum is not correct and should be dismissed.