Early observation of the aurora australis: AD 1640

Extract

The Chilean Jesuit Juan Ignacio Molina SJ presented evidence for the occurrence of a large auroral display in 1640, which was allegedly seen every night in the Araucanía region of Chile from the beginning of February to the end of April. The relevant evidence was presented briefly in a book on the natural history of Chile published in 1782, almost one-and-a-half centuries after the original observation. Our search through the chronicles of Chilean history recorded in both Spanish and Latin-American literature has uncovered copies of the original publications by two earlier Jesuits, Alonso de Ovalle SJ and Diego de Rosales SJ, which describe a “battle in the sky” and a “volcanic eruption”. The available historical evidence is interpreted scientifically in terms of the coincidence of two separate optical phenomena over a period of three months (February-April). These two phenomena can be explained in terms of essentially continuous optical emission resulting from the volcanic eruption and more variable optical emission resulting from intermittent auroral displays associated with intense recurrent geomagnetic activity.