A low latitude Auroras catalogue from 1766 to 1797 (Padua, Italy)

Abstract:

It is presented a long term catalogue of aurorae from the observations done by Joseph Toaldo between 1766-1797 at La Specola (the Observatory) in Padua (Italy, 45º24’07.5’’N, 11º52’06.8’’E). Toaldo was interested in astrometeorology and was the prime mover and the first director of the Astronomic Observatory where he carried out valuable daily observations on both fields. He also taught astronomy and meteorology at the University of Padua.

The data was collected from different historical document sources including the original manuscripts made by Toaldo which also contain meteorological readings. A total of 148 aurorae events were recovered from Toaldo's manuscripts. The data reliability was validated using time and season, percentage of the moon illuminated and aurorae directionality.

The data shows a secular maximum of the auroral activity around 1780 that occurred at planetary scale. From 1789 onwards there is a sharp decrease of this activity marking the onset of the Dalton Minimum although the solar activity decreases less rapidly. It has also been collected geomagnetic declination measurements taken in Padua between 1725-1799. These geomagnetic observations are consistent with the geomagnetic model gufm1.