Midday auroras at the south pole during magnetospheric substorms

It is shown that there is a close relationship between the range of the equatorward shift of the midday aurora and the magnitude of a negative bay at an auroral-zone station in the midnight sector. Their time variations are also similar. This relationship can be taken to be a clear indication of a close association of magnetospheric substorms with the transfer of the magnetic flux from the front of the magnetosphere to the magnetotail. Furthermore, the intensity of magnetospheric substorms appears to be approximately proportional to the net amount of transferred magnetic flux.