Some aspects of the interaction of interplanetary shocks with the Earth’s magnetosphere: an estimate of the propagation time through the magnetosheath

We analyzed a number of forward shocks detected by Wind in the interplanetary medium to determine the orientation and speed of the shock fronts. Assuming a planar shock geometry and a constant propagation speed (both confirmed by a comparison with available Geotail observations), we determined when the shock would hit the bow shock (BS) and evaluated the propagation time of associated disturbances between the BS and ground. We found delay times were similar to 5 min: for almost radially propagating structures, this delay time would imply magnetosheath speeds of shock associated disturbances of similar to1/3-1/4 of the external shock speed.