Responses of the ionospheric electric field to the sheath region of ICME: A case study

We have examined the response of ionospheric electric field to the ICME sheath with the coordinated ground- and space-based magnetic measurements during the initial phase of December 14, 2006 storm. The duskward IEF pulses enhanced the westward convection electrojet and the eastward equatorial ionospheric electric field. The in situ magnetic measurements in the vicinity of geosynchronous orbit suggested that the Earth’s magnetosphere was continuously compressed on the dayside and stretched to more tail-like on the nightside, due to the sustained high solar wind dynamic pressure in the sheath region. The compression prevented shielding current from increasing and then caused electric field penetration.