Prompt GPS TEC Response to Magnetospheric Compression by Interplanetary Shock

A new type of total electron content (TEC) variation was observed in prompt response to an interplanetary shock (IS) impact on the Earth's magnetosphere. With hundreds of ground-based global positioning system (GPS) receivers, simultaneous TEC impulses with amplitudes as large as 0.3 TECU were detected in the signals of GPS satellites which were cruising in the dayside equatorial magnetosphere. We suggest that the TEC impulses result from shock-induced magnetospheric compression, which drives plasma to move earthward via perturbed electric field in the dayside magnetosphere. The observed TEC increase reflects the radial motion of plasma from outside of the GPS orbit (4.2 RE) to inside, showing an unprecedented ability of the GPS TEC technique to capture small tremor of the magnetosphere and, with the dense receiver network it can be a useful tool for investigating the plasma dynamics around 4.2 RE.