Individual daytime traveling ionospheric disturbances (TID's) in the F‐layer are studied using three ionosondes mutually approximately 150 km apart in northern New Hampshire and Vermont. The ionosondes were operated continuously for long periods of time, making ionograms every two minutes. Methods of scanning the continuous data for TID's, and of analyzing them, are described. Iso‐height contours are emphasized as superior to iso‐ionic contours for analysis. It is found that the direction toward which a TID travels is essentially independent of height within the disturbance and that the directions of travel cluster about the south‐southeast. Other parameters are found to be height‐dependent and will be the subject of future papers.
Hooke (1968) developed a formula for the perturbation of electron density in the F2 region of the ionosphere by any spectral component of a gravity wave, the perturbation being manifested as the corresponding spectral component of a traveling ionospheric disturbance (TID). We have used the phase portion of that formula to obtain the real part of the vertical component of the propagation constant of the causative gravity wave from that of a TID. With this we have compared the amplitude portion of Hooke's formula with the observed TID amplitude. Doing this over a range of height within a particular TID, we find relatively good agreement. It is suggested that further improvement would require using an electron density perturbation formula which takes account of ion diffusion.
This paper reports on an international comparison of surface-texture parameters, , and , carried out between nine national metrology institutes from 1996 to 1998 under the auspices of the Asia-Pacific Metrology Programme (APMP) and coordinated by the CSIRO National Measurement Laboratory (NML, Australia). The results show that the consistency of the measurements is generally better than that of the and measurements, which appear to split into two sub-groups with some crossover. Agreement is somewhat better for artefacts of higher surface roughness. Measurements of step height were also made as a potential indicator of correlation between the basic length scale and the surface-roughness parameters. These show satisfactory agreement, within the stated uncertainties and with the normalized error, , values <1 in all cases.
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