Variations in GPS TEC associated with magnetic field line resonance activity in the early morning auroral ionosphere

Abstract:

Observations of ionospheric total electron content (TEC) variations associated with magnetic field line resonance activity (FLR) in the Pc5 (1.7 to 6.7 mHz) frequency band are presented. TEC measurements are from the Sanikiluaq, Nunavut (56.54ºN, 280.77ºE) Global Positioning System (GPS) receiver of the Canadian High Arctic Ionospheric Network (CHAIN), which is located in the auroral region. Over a period of 3.5 hours in the early morning, continuous TEC variations at Pc5 frequencies are concurrently observed with Pc5 band FLR activity observed by the geosynchronous GOES 13 satellite magnetometer and the ground magnetometer in Sanikiluaq. Spectral analysis indicates a narrow band of dominant Pc5 frequencies in the GOES magnetic field variations, with a broadening of the spectral distribution in ground magnetic field and TEC variations. The dominant frequencies observed on the ground and at GOES agree with the calculated fundamental mode FLR eigenfrequency. Amplitudes of TEC variations range from 0.1 - 2 TECU, and are most likely a result of energetic particle precipitation modulated by the Pc5 FLR. Further, GOES 13 particle measurements show flux variations for >30 keV electrons located in the atmospheric loss cone during the largest amplitude TEC variations. These flux variations are of similar frequency to the TEC variations. In addition, measurements from multiple GPS satellites are used to examine the phase delay of FLR-associated TEC variations in the longitudinal and latitudinal directions. Due to the high temporal and spatial resolution of GPS TEC measurements, detection of ULF waves by GPS TEC is a potentially useful tool in the study of ULF properties and the associated ionospheric response.