Interaction between an interplanetary magnetic cloud and the Earth's magnetosphere: Motions of the bow shock

An interplanetary magnetic cloud (IMC) is an important solar‐terrestrial connection event. It is an ideal object for the study of solar‐terrestrial relations and space weather because the Earth's space environment can be affected considerably during an IMC passage. An IMC was observed to pass the Earth during October 18–20, 1995. Wind recorded its interplanetary characteristics at ∼ 175 RE upstream of the Earth's bow shock, and ∼ 45 min later, Geotail, being near the nominal location of the dawn bow shock, detected IMC‐related multiple bow shock crossings. Using simultaneous measurements from Wind and Geotail, we analyzed, with a semiempirical bow shock model with two parameters, the bow shock motion caused by the interaction of the IMC with the magnetosphere during the passage. We also compared the bow shock motion predicted by the model, and hence the predicted Geotail bow shock crossings, with Geotail observations of the actual crossings. The results showed that the observed multiple bow shock crossings, which were obviously due to temporal variations of the upstream solar wind, can be well explained by the model‐predicted bow shock motion.