Conjugation of geomagnetic field lines at magnetic high latitude is variable, depending on solar wind and interplanetary magnetic field conditions. In this paper the geomagnetic conjugate point of a location under closed field lines near the cusp has been determined dynamically by examining the conjugate phase relation of ultra low frequency (ULF) waves in the Pc5 band using magnetometer data from high-latitude ground stations at Longyearben (LYR), Hornsund (HOR), and Hopen Island (HOP) in the Northern Hemisphere and Davis (DAV), Zhongshan (ZHS), and Mawson (MAW) in the Southern Hemisphere. Cross-spectral and coherency analysis methods are used to select conjugate Pc5 events and derive phase relations. The results show that near the cusp the geomagnetic field lines resonate mainly in the odd mode with the D component out of phase and the H component in phase, when observed at the two ends of the field line. Assuming this phase characteristic, the conjugate of LYR is typically located in the DAV/ZHS-region and mainly east of Davis by about 10° CGM longitude. In a reverse mapping analysis the conjugates of ZHS and DAV are located in the LYR region, mainly west of LYR by 10°. These results are qualitatively consistent with corresponding locations derived from the Tsyganenko  (T96) model. The relationship of the longitude movement of the conjugate of LYR with respect to the variation of IMF By is quantitatively consistent with the T96 model. However, the expected position of the conjugate site of LYR (DAV/ZHS) derived from Pc5 phase for By = 0 is moved westward (eastward) by about 10° CGM in longitude or ~300 km from that predicted by the T96 model.
Journal of Geophysical Research: Space Physics Vol. 108, Issue A7, p. 3-1-3-16