In two ~1 hr case study periods, the properties of whistlers propagating along multiple geomatnetic-field aligned paths from points of origin in the northern hemisphere were compared to data on the location and intensity of lightning. The whistlers were recorded at the approximately conjugate stations Lake Mistissini, Canada and Siple Station, Antarctica, while the lightning data were acquired by the SUNY-Albany lightning detection network operating in the eastern United States. In the two studies, which represented times near 0700--0800 LT and relatively quiet magnetospheric conditions, between one quarter and one half of the two-hop whistlers observed at Lake Mistissini were found to have originated in ground flashes detected by the network. The uncorrelated whistlers are believed to have originated in lightning outside the network viewing area or in undetected ground flashes within the network. However, intracloud flashes within the network area cannot be ruled out as causes of some of the uncorrelated events. We confirm evidence from other workers that lightning can excite ducted whistler paths whose ionospheric endpoints are at ranges up to 2500 km or more from the lightning location.

Once in the magnetosphere, the ducted waves were found to ''spread'' in L value by an interpath coupling process that was operative over the entire L range detected whistler paths (~1000 km in the north-south direction at ionospheric heights in one case and ~1500 km in the other). In both cases there was a single most active whistler path at L≂4.7, at the high-L mimit of propagation paths within the plasmasphere. In one of the cases, lightning at L≂1.6--1.8 illuminated this path through interpath coupling, after first exciting a path at L≂2.2. In the other case, each of 15 flashes in a storm center at L≂3.5 excited the path directed at a range of roughly 600 km. An approximately linear relation was found between the normalized first stroke peak magnetic field (which is proportional to the peak current) and whistler amplitude observed during a 10-min period. The detection of whistler waves on a particular magnetospheric path and the relative intensity of the waves in successive whistlers appear to be strongly dependent upon the field strength of the impulsive radio signal from lightning at the point of ionospheric wave injection. Meanwhile, the distribution in space of the multiple paths, the absolute wave levels on the various paths, the duration of propagation in terms of higher order echoes, and the interactions of whistlers and VLF emissions propagating on the same path are found to depend primarily upon magnetospheric propagation conditions.

For example, on both days the path transmitting the most whistler wave energy to a ground receiver was the one with entrance point the most distant from the lightning source. ¿ American Geophysical Union 1989