Climatology of ionospheric perturbations associated with Pc3-6 ULF waves, as observed using ground-based GPS total electron content measurements

Several case studies have revealed fluctuations in ionospheric total electron content (TEC) associated with ultra-low frequency (ULF) magnetic field variations observed using satellite and ground magnetometers. At this point, the TEC response to ULF waves is considered unpredictable and intermittent, and the mechanisms that drive the variations in TEC are still unresolved. We have conducted a survey of the TEC response to ULF waves in the Pc3-6 (up to 200 mHz) frequency range using high-data-rate Global Positioning System (GPS) receivers of Sanikiluaq (56.54⁰N, 280.77⁰E) and Fort Simpson (61.76⁰N, 238.77⁰E) stations, located in the auroral region of the Canadian Arctic. In-situ ULF activity was monitored using magnetometer measurements of the GOES 13 and 15 satellites, which have magnetic footprints near Sanikiluaq and Fort Simpson, respectively, while corresponding ULF activity on the ground was monitored by Sanikiluaq and Fort Simpson ground magnetometers.

A survey of ULF wave events during the years 2015-2017 revealed 1221 narrow-band Pc3-6 ULF waves observed by the GOES magnetometers, during periods where simultaneous GPS TEC and ground magnetometer measurements were also available. Cross-spectral analysis of GOES satellite magnetic field fluctuations with those of GPS TEC and ground magnetic field was used to determine whether variations observed in the respective measurements were linked. Discrete peaks in GOES ULF wave occurrence were observed in the morning, afternoon, and nighttime sectors, with peak seasonal occurrence around December solstice. Overall, coherent fluctuations in GPS TEC were observed in 15% of GOES ULF wave events. Of these TEC events, 92% were accompanied by coherent variations in ground magnetic field, while 8% had no corresponding magnetic field variations on the ground. Other major factors governing the TEC response to ULF activity will also be discussed, including ULF wave polarization, season, local time, and background ionospheric conditions.