Resumen
Auroral observations of equatorward extent of the rayed auroral displays are researched. Ground-based observations at Belgrano Station (78.0º S; 38.8º W) during the southern winter months of 1981 are considered. Four hourly sequences of geomagnetic indices AE, AL, AU and PC, the interplanetary magnetic field (IMF) and relevant solar wind parameters are superposed for 18 substorms. The present work confirms (during the 240 minute intervals centered at the sudden equatorward shift event) the relationships existing between the southward interplanetary magnetic field component (Bz), and the auroral occurrence of substorms and the westward auroral electrojet intensity.