GPS TEC response to Pc4 “giant pulsations”

Abstract

Variations in ionospheric total electron content (TEC) associated with ultralow frequency (ULF) magnetic field variations in the Pc4 (6.7–22.0 mHz) frequency band were observed in the early morning sector. TEC variations were observed by the Global Positioning System (GPS) receiver in Sanikiluaq, Nunavut (56.54°N, 280.77°E), which is located near the equatorward edge of the auroral region. Small‐amplitude Pc4 ULF waves were observed by the Sanikiluaq ground magnetometer and by the geosynchronous GOES 13 satellite. TEC and magnetic field both exhibited narrowband, highly regular, quasi‐sinusoidal waveforms, with high correlation and coherence indicating a clear link between TEC variations and Pc4 ULF activity. Variations in TEC and 30–50 keV electron flux observed by GOES 13 were also highly correlated and coherent. TEC variations observed directly above Sanikiluaq were in antiphase with eastward magnetic field variations on the ground, while TEC variations observed at the footprint of the GOES 13 satellite were in phase with GOES radial magnetic field and 30–50 keV electron flux. Intermittent occurrence of TEC variations observed by multiple GPS satellites indicated a localized ionospheric response to the Pc4 activity. This is the first clear evidence of a TEC response to these so called “giant pulsations (Pgs).” By applying a multisatellite triangulation technique, the phase velocity, group velocity, and azimuthal wave number of TEC variations were also calculated for an interval of highly coherent measurements. The phase and group propagation velocities were 2–7 km/s and 1–3 km/s north and westward, respectively, while the azimuthal wave number ranged from −35 to −310.

A case study of correspondence between Pc1 activity and ionospheric irregularities at polar latitudes

“…1, upper panel). It is worth noting that, in a recent study, Watson et al (2016) found a clear link between TEC fluctuations and geomagnetic field fluctuations in a frequency range much lower (6.7-22 mHz) than that analyzed in our study (0.2-1 Hz).…”

Ionospheric Plasma Density Oscillation Related to EMIC Pc1 Waves

“…This expectation, however, has not yet been confirmed observationally due to the lack of sufficient in situ data. Until now, only ULF Pc3-Pc5 waves (2-100 mHz) have been reported to accompany pulsations of ionospheric total electron content (TEC) in similar frequency ranges (Belakhovsky et al, 2016;Davies & Hartman, 1976;Okuzawa & Davies, 1981;Pilipenko, Belakhovsky, Kozlovsky, et al, 2014;Pilipenko, Belakhovsky, Murr, et al, 2014;Vorontsova et al, 2015;Watson et al, 2015Watson et al, , 2016.…”

Climatology and Characteristics of Medium‐Scale F Region Ionospheric Plasma Irregularities Observed by COSMIC Radio Occultation Receivers

“…Kelley () defined “mesoscale” structures as ionospheric irregularities with scale sizes of 50–1,000 km horizontally and 0.5–50 km vertically. Most Global Navigation Satellite System (GNSS) studies of plasma irregularities have employed ground‐based receivers, which provide the high‐resolution structure and propagation in the horizontal dimension (Jayachandran et al, ; Pilipenko et al, ; Watson, Jayachandran, Singer, et al, ), but miss out on critical information pertaining to the vertical irregularity structure and are primarily limited to landmasses. Global radio occultation (RO) measurements from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) provide a valuable opportunity to address this observational gap.…”