Local time variation of geomagnetic induction vectors

Abstract

Geomagnetic induction vectors are calculated in four frequency bands (between 0.72 and 27 mHz) at 2‐hour intervals for 12 consecutive days from data acquired at four magnetic stations spaced between ∼54° and ∼65° geomagnetic latitude near geomagnetic longitude 4°W. Significant temporal variations are found in the local time dependence of the induction vectors even when they are averaged over appreciable time periods. These variations in the induction vectors are qualitatively related to measured local time changes in the power spectral amplitudes and ellipticities during the 12‐day period. Time‐intensity data plots and wave polarization diagrams are presented that demonstrate the great variability in the magnetosphere sources in the frequency intervals studied. The present results and discussions call into question assumptions commonly made in the straightforward derivation and use of geomagnetic induction vectors for defining internal conductivity structures.