... Magnetospheric whistler waves were first observed by Storey (1953), who interpreted them as evidence of plasma around Earth. ... Whistlers have also provided an indirect way to estimate plasmaspheric electric fields (Carpenter et al., 1972). This is because the whistler ducts move radially under the influence of the azimuthal electric field. ... Carpenter, D. L., K. Stone, J. C. Siren, and T. L. Crystal, Magnetospheric electric fields deduced from drifting whistler paths, J. Geophys. ...