Low-latitude ducted whistlers observed at Sanya, Hainan, China

Observations of whistler, multiwhistler, and tweek received at Sanya (18.24 N, 109.5 E; magnetic latitude 7.04 N) China are discussed. The physical features of low-latitude whistlers are studied. Results show that ducted whistlers propagating along the field-aligned ducts can be received at low latitude, and that whistler ducts also exist in the ionosphere. The critical cut-off latitude of ducted whistlers may be located at the region with a magnetic latitude 7.04 N.