Auroras boreales observadas en la Península Ibérica, Baleares y Canarias durante el siglo XVIII

Abstract

Aurorae observed in the Iberian Peninsula and the Balearic and Canary Islands, during the XVIIIth Century
A reasoned catalogue of aurorae borealis is shown in the present paper. They were observed in geographical latitudes relatively low for the phenomena (28º-43º) and for a lapse of time scarcely explored. The 80 observed aurorae have been collected by means of abundant unpublished information found in specialised literature and their critical treatment, increasing considerably their number up to now. All aurorae borealis took place between the years 1716 and 1792, a period of time that coincides with the great solar activity displayed between the Maunder and Dalton minimums. There was a void interval between 1737 and 1764 being uneven the distribution between the two subperiods. The fluctuations of the auroral oval can explain the disappearance of aurorae between 1737 and 1764 and also the observations in the Canary Islands between 1770 and 1778. The good correlation with the circadecennials solar cycles and the circamonthy solar rotation has been proved, however the Rieger periodicity has not been detected. The catalogued observations are coherent with the lunar phases and the well-known equinoctial cycles. Reasoned catalogues show some advantages in the studies of auroral activity, because: a) integrates all the information available; b) allow to correct errors and voids of information in the initial data; and c) provide a fitted view of the history of the auroral activity in the studied area.