A possible mechanism for echo striation generation of radar backscatter from midlatitude sporadic E

摘要

The morphological resemblance is described between the quasi-periodic scintillations of VHF radio wave transmissions from a satellite and the 46.5-MHz radar backscatters of the middle and upper atmosphere (MU) radar radio waves, which are both associated with ionospheric irregularities in the sporadic E layer. Because these observation techniques are sensitive to different wavelengths of irregularities, the resemblance may be caused by coexisting irregularities. That is, radio wave scintillations reveal medium-scale density-enhanced regions with a specific scale length of several hundred meters in which small-scale irregularities are embedded. The MU radar echoes may reveal backscatter signals from small-scale irregularities. A periodic structure on a range-time-intensity (RTI) map reflected the spatial structure of the medium-scale density-enhanced regions. A model is proposed to explain the striations on the RTI map, which extend up to heights of several tens of kilometers even though sporadic E layers are usually thin.