Electrical conductivity of the lowermost mantle explains absorption of core torsional waves at the equator

摘要: Torsional Alfven waves propagating in the Earth's core have been inferred by inversion techniques applied to geomagnetic models. They appear propagate across but vanish at equator, exchanging angular momentum between and mantle. Assuming axial symmetry, we find that an electrically conducting layer bottom of mantle can lead total absorption torsional reach equator. We show reflection coefficient depends on G Br , where is strength radial magnetic field conductance lower there. With = 7e-4 T., are completely absorbed when they hit equator if 1.3e8 S. For larger or smaller G, occurs. As increased above this critical value, there less attenuation more exchange. Our finding dissociates efficient core-mantle coupling from strong ohmic dissipation