TY JOUR TI Asymmetry in occurrence of the leading and following polarities in the photospheric magnetic field at the early stage of active region formation KW magnetic field KW active regions JO Solar-Terrestrial Physics AU Grigoryev, V.M. AU Ermakova, L.V. AU Khlystova, A.I. PY 2020 IS 6 PB INFRA-M Academic Publishing LLC.