Proceedings with Extended Abstracts (single PDF file) - Radio ...

LARGE VELOCITIES MEASURED AT MF AND HEIGHTS ABOVE100KM: REAL OR SPURIOUS ?Chris Meek and Alan MansonInstitute of Space and Atmospheric StudiesUniversity of Saskatchewan, CanadaAbstract: The MF data set for Saskatoon has been scanned for large speeds (e.g. greater than150 m/s). These data are not numerous and usually occur at heights greater than we normallyuse. They are usually excluded from most analyses by our upper speed selection limit of170m/s, by rejection of signals above the height of maximum signal (assumed to beobliques), or by our virtual height limit criterion: viz. reject heights greater than 94/105 Kmin summer/winter. The latter is necessary in tidal analysis to insure that the daytime andnighttime data refer to the same real height.Here we look at these large wind values separately, but due to lack of space, we can showonly winter data. In winter they tend to occur in the late afternoon, are not spurious, and alsocontain a tidal signal (in seasonal averages). Data from a separate experiment (a non-coherentsystem run in winter 1987-88) which looked for signal peaks from 70-355 Km virtual height)are used to argue that we can sometimes see through the daytime E-region.Discussion:Figure 1. Sample of the 1987 local signal peak dataFigure 1 shows a sample of the 1987 local signal peak data; the time resolution is ~20 sec.Echoes above the E region are most common around 20-22 UT (mid afternoon). These arenot multiple hop, since otherwise we would see a lower echo as well. Some F-regionsplitting (e.g. day 336/01-03 UT) is seen, probably O and X since the experiment used linearpolarization.238