Simultaneous observation of whistlers at two Lapprox. =4 Alaskan stations

In an attempt to understand the scatter produced by east-west gradients in whistler-deduced radial profiles of equatorial electron density in the outer plasmasphere, maps of electron densities have been produced in L-LMT (local magnetic time) polar coordinate space as the whistler stations turn through LMT. Simultaneous observations at two Lapprox. =4 Alaskan stations, 1.6 hours apart in LMT, are found to result in identical maps, in-phase in LMT, on two of the three occasions studied, revealing that the density contours, like the plasmapause itself, were stationary in L-LMT space and were unchanging in the 1.5 hours of UT elapsed between the tracing of the map first by the eastern station and then by the western station. On the third occasion the maps are quite different, suggesting that strong east-west gradients existed between the stations and were corotating with them. Maps of persistent whistler duct tracks constructed from the same data points in L-LMT space are found to be identical between the two stations on all three occasions. Individual whistlers from the same causative sferic occur simultaneously at the two stations but at the same LMT. The conclusion is that the individual ducts, though thin in the cross-L direction, are extensive in the east-west direction, standing in a stationary pattern in L-LMT space; or that a succession of tubular ducts stands along such tracks, possibly corotating with the earth along the stationary tracks. Direction finding at two stations may help to determine which interpretation is correct. If the contours are equipotential plasma flow lines, their apparent radial movement seen by a single station turning under them gives the correct rate of radial flow only if the eastward component of flow along them is exactly corotational with the earth