The Properties of the Tilts of Bipolar Solar Regions

Abstract

We investigate various properties associated with the tilt of isolated magnetic bipoles in magnetograms taken at the solar surface. We show that bipoles can be divided into two groups that have tilts of opposite signs, and reveal similar properties with respect to bipole area, flux, and bipolar moment. Detailed comparison of these physical quantities shows that the dividing point between the two types of bipoles corresponds to a bipole area of about 300 millionths of the solar hemisphere. The time-latitude distribution of small bipoles differs substantially from that for large bipoles. Such a behaviour in terms of dynamo theory may indicate that small and large bipoles trace different components of the solar magnetic field. The other possible explanation is that the difference in tilt data for small and large bipoles is connected with spectral helicity separation, which results in opposite tilts for small and large bipoles. We note that the data available do not provide convincing reasons to prefer either interpretation.