Anomalous DS-variation in equatorial latitudes during geomagnetic storms

For several storms the asymmetry of the magnetic disturbance values at equatorial latitudes has been investigated. Asymmetries were found for which the maximum and minimum depressions of the horizontal intensity occur at midnight and at noon, respectively, (anomalous DS-variation); other asymmetries, where the maximum and minimum depressions were observed in the morning and in the evening, respectively (inverse DS-variation). The DS-variation at equatorial latitudes was discussed in connection with the polar magnetic substorm and the D_st-variation.