The local time asymmetry of the geomagnetic disturbance field at low latitudes and its dependence upon the interplanetary activity.

Using 3-minute data of magnetic observations, the asymmetric magnetic disturbance field in lower latitudes is calculated for 4 different storms and the dependence of this asymmetry on the activity of solar wind and interplanetary magnetic field is investigated. Different asymmetry parameters, separate for the geomagnetic X- and Y-component, are calculated. The LT profiles of the DS-variation in the geomagnetic X- and Y-component resemble those of the model of CROOKER and SISCOE (1981) and not those of CLAUER and MCPHERRON (1980). The dependence of the intensity of the asymmetry on the interplanetary electric field and on the ε-parameter is also investigated. The cross correlation function among the corresponding time series has been calculated. Maximum correlation is obtained with a shift of 45 to 100min. Here, the four storms investigated showed different correlation of the corresponding parameters ranging from 0.5 to 0.9. It can be supposed that the observed asymmetry is a consequence less of a partial ring current than of a current system described by CROOKER and SISCOE (1981). The phase of the DS-variation in low latitudes is not influenced by interplanetary disturbances. This means that in addition to interplanetary processes, magnetospheric processes also are responsible for the generation of the asymmetric disturbance field.