GPS–TEC response to the substorm onset during April 5, 2010, magnetic storm

We consider disturbances of total electron content (TEC) of the high-latitude ionosphere provided by the GPS global navigation satellite system before and during the magnetic storm on April 5, 2010. Simultaneously, we examine magnetic data from all available magnetometer arrays in the northern hemisphere, augmented with data from scanning photometers and riometers. The substorm onset, during both non-storm and storm periods, is found to cause significant enhancement of TEC scintillations characterized by the TEC time derivative dTEC. Comparison of 2D maps of the spectral power of magnetic fluctuations in the Pc5 band (1–10 mHz) and dTEC during substorms shows a good spatial and temporal correspondence between them. Both magnetic and ionospheric fluctuations tend to concentrate inside the auroral oval, the boundaries of which are determined from the OVATION model. The time–space evolution of TEC scintillations is rather similar to that of ultra-low-frequency magnetic fluctuations, but not to that of the ionospheric electrojet. GPS signal phase slips, resulting in non-physical TEC jumps (>1 TECu/min), occur predominantly inside the auroral oval and in the vicinity of its equatorward boundary.