Position of the Source of Dayside High-Latitude Magnetic Impulses in the Magnetosphere from DMSP Satellite Data

Dayside high-latitude geophysical phenomena provide a ground-based observer with information about the processes at the dayside magnetopause and/or in the adjacent magnetospheric domains. It is assumed that these phenomena are initiated by changes in the parameters of the interplanetary medium and can therefore be used as a tool to investigate the ways in which solar wind energy penetrates through the magnetopause. Such phenomena include magnetic impulses, which are an isolated train of damped oscillations of two to three bursts with a repetition period of 8–12 min. Eight magnetic impulse events were investigated using data from the Scandinavian IMAGE magnetometer network, for which DMSP satellites flew over the observation area during, shortly before, and immediately after the impulse and crossed the boundaries of several domains. From ground-based and DMSP satellite data, it is shown that the downward field-aligned current associated with the impulses is located away from the magnetopause. This means that the impulse cannot be considered as an ionospheric trace of a reconnected flux tube (flux transfer event, FTE) and/or as a traveling convection vortex (TCV). It is found on a larger statistics that the impulse is preceded by marked changes in the By- and Bz-components of the IMF, while the contribution of rapid changes in solar wind pressure and velocity as well as in the Bx-component of the IMF to the generation of the magnetic impulse is not obvious. A possible scenario of the magnetic impulse initiation by IMF variations is discussed.