Variations in the occurrence frequency of Aurora in 1837–1900 from data of the Russian network of meteorological observatories

Abstract

Observations of auroras in Russia from 1837 to 1900 have been catalogued on the basis of data of the Russian network of meteorological observatories. These observation data from 129 stations in the European and Asian parts of Russia cover a wide geographical zone (ϕ = 39°57′–72°30′ N and λ = 21°1′–224°35′ E). A difference was revealed between the behavior of midlatitude (Φ < 56°) and high-latitude auroras during a solar cycle. A peak in the occurrence frequency of aurora dominates at the cycle maximum in midlatitudes; there is an additional maximum during the declining phase. In contrast, the dominant occurrence frequency peak is observed during the declining phase of a solar cycle or at its minimum for high-latitude auroras. In addition, the occurrence frequency of high-latitude aurora increases in 1837–1900. An upward trend in the occurrence frequency of aurora is also observed at the St. Petersburg observatory (Pavlovsk, Φ = 56°). This trend apparently is evidence of an increase in the open regions of solar magnetic fields in 1837–1900. Some parameters of auroral activity also show a 22-year variation.