Hemispherical asymmetries in sunspot areas and auroral frequencies

Abstract

One thousand and fifty-two aurorae boreales and 554 aurorae australes recorded during the nineteenth century at medium latitudes ≦ 55° N or ≦ 55° S are compared statistically with the known hemispherical asymmetry of the sums of the areas of sunspots. According to the present study, the solar hemispherical asymmetry may be accompanied by an analogous pattern of the hemispherical frequency of auroral days. For the number of auroral days in each hemisphere beyond the two auroral ovals, a remarkable degree of phase equality with the sunspot areas during the second Gleissberg cycle can be demonstrated.