SPATIAL STRUCTURE AND POLARIZATION OF GEOMAGNETIC-PULSATIONS OBSERVEDON THE GROUND

At low latitudes, the phase of H component of the ground magnetic pert urbation can be expected to be independent of the latitude for low-fre quency geomagnetic pulsations. Because of such a spatial phase structu re of the H component, it is found that the D component has a 180 degr ees out-of-phase relation between the northern and southern hemisphere s and its amplitude increases monotonously from the magnetic equator t o higher latitudes. It is also shown that the sense of rotation of the magnetic perturbation vector in the H-D plane is clockwise and counte rclockwise for the eastward and westward propagations, respectively, i n the northern hemisphere and vice versa in the southern hemisphere. O n the other hand, since the spatial phase structure of the H component far away from the magnetic equator becomes more complicated as the la titude increases, the correlation between signal propagation sense and horizontal polarization may deteriorate at high latitues. For the amp litudes of H and D components due to the compressional component of th e magnetic field incident upon the ionosphere their upper bounds are a lso given.