Leo F. McNamara

Values of hmF2 deduced from automatically scaled ionograms

Abstract The values of hmF2 deduced by real-height analysis of automatically scaled vertical incidence Digisonde ionograms have been compared with those obtained using simple methods based on routinely scaled ionospheric characteristics. Comparisons have been made for ionograms recorded at five stations during low solar activity. The real-height analyses used Titheridges program POLAN, while the simple methods used were those of Dudeney and Bilitza. Systematic discrepancies between the simple-model and POLAN values of hmF2 were found, with 15–20 km overestimates of hmF2 by the simple methods during the night. The majority of discrepancies lie between ±20 km. During the day, 80% of discrepancies lie between ±10 km. Significantly larger discrepancies can usually be attributed to special ionospheric conditions or ionograms, failure of the automatic scaling technique, or failure of one of the basic assumptions of the simple models.

Statistical studies of the N(h) profile of the ionosphere using automatically scaled digital ionograms

Abstract The advent of digital vertical incidence ionosondes and automatic scaling has brought with it the capability of performing large-scale analyses of the detailed structure of the ionosphere. In this paper, we use about 6,000 Digisonde 256 ionograms recorded at Millstone Hill, Massachusetts during 1988 and scaled automatically by ARTIST, to investigate relationships which exist between various profile parameters and to investigate the accuracy of estimates of these parameters based on simple models of the ionosphere. In particular, we (1) confirm for the mid-latitude ionosphere the high level of accuracy of the Dudeney formula for hmF2, (2) illustrate the limited utility of Gulyaevas value for the height at half the peak density, and (3) illustrate the relationship between the semi-thickness of the F2 layer and the value of hmF2.