A new type of mid-latitude multi-path whistler trains including a non-ducted whistler



This paper reports on a new type of midlatitude multi-path whistlers based on the observations at Hobart, Australia and Dunedin, New Zealand. Though a majority of whistler elements are ducted, this new type includes a non-ducted whistler as well. The study is based on the detailed comparison of the field-analysis direction finding results with the nose-extension ones. Important findings have emerged from this study and are summarized as follows. (1) A majority of whistler elements are ducted, (2) the duct dimension is highly likely to be less than 50km in diameter, (3) the ducts are likely to be extended well down to the ionospheric region, (4) the whole life of ducts seems to be of the order of 6 hours, with including cyclic occurrence and decay, and (5) at least one whistler element was experimentally convinced to be a non-ducted PL whistler.