Large-amplitude GPS TEC variations associated with Pc5–6 magnetic field variations observed on the ground and at geosynchronous orbit

摘要

Large-amplitude variations in GPS total electron content (TEC) at Pc5–6 (<6.67mHz) frequencies have been observed, using a high data rate Global Positioning System (GPS) receiver of the Canadian High Arctic Ionospheric Network. TEC variations with peak-to-peak amplitudes of 2–7 TEC units (1 TECU= 10~(16) elm~(-2)) were observed over a 2.5 h period in the postnoon sector on 9 September 2011, during a period of high auroral activity within a moderate geomagnetic storm. TEC observations were from the Sanikiluaq, Nunavut (56.54°N, 280.77°E) GPS receiver located in the auroral region. Over this same time period, compressional Pc5–6magnetic field variations were observed by the geosynchronous GOES 13 magnetometer and the ground-based Sanikiluaq magnetometer. GOES 13 has a northern magnetic footprint in close proximity to Sanikiluaq. Cross-correlation analysis indicates that magnetic field and TEC variations were possibly linked. No natural hazards or nuclear explosions capable of exciting TEC perturbations were reported on this day. Using a triangulation technique involving TECmeasurements ofmultiple GPS satellites, the propagation velocity of TEC variations in the ionosphere was also calculated. This calculation revealed two distinct events: lower frequency (~0.9mHz) TEC variations that propagated westward, consistent with the westward propagation of compressional Pc5 waves observed by GOES 13 and 15 satellites, and higher-frequency (~3.3mHz) TEC variations that propagated southward. This is the first report of variations in ionospheric TEC linked to satellite observations of Pc5–6 ULF waves.