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

Figure 3 shows winds for a composite winter day (Nov.-Feb.) – the arrows represent anaverage of all 5-minute raw wind vectors with speeds greater than 150 m/s and the lines thosewith speeds less than 100 m/s. The former have numbers in the 10s and 20s, while the latterhave numbers in the 100s and 1000s. Individual vectors from the first set often had speeds ashigh as 400-500 m/s.Comparison between the two sets of winds in Figure 3 suggest that, while there are someconsistent differences in direction, these large speeds merely represent the upper end of thespeed distribution, and are not a different phenomenon. The differences in direction could bedue the few isolated events of high winds not matching the long term average direction. Inboth sets there is a significant vector rotation with height around noon, which indicates a realchange in height rather than oblique echoes from a total reflection layer. However, theheights still must be assumed to be virtual - i.e. affected by retardation.The clockwise (CW) rotation in time suggests the presence of a 12 hr tide (because the windhas similar directions 12 hours apart) while the rotation in height, also CW with increasingheight, is as expected for downward phase propagation. The majority of high speed casesoccur around noon (19 UT).Conclusion: This shows that the spaced antenna MF experiment can measure large speeds -even larger than would be expected, given the experimental parameters, such as antennaspacing (156m), and sample time (0.5s). In most cases the vectors appear to be consistent indirection with the all-wind average (not shown). On the whole it appears that the largeheights, nominally above the E region, are probably virtual, and can be attributed toretardation within the E-region.240