Morphology of quantified ionospheric range spread-F over a wide range of midlatitudes in the Australian longitudinal sectorReport as inadecuate




Morphology of quantified ionospheric range spread-F over a wide range of midlatitudes in the Australian longitudinal sector - Download this document for free, or read online. Document in PDF available to download.

1 Department of Physics

Abstract : Ionograms from a standard vertical-incidence ionosonde chain nine stations, obtained over a wide range of southern latitudes in geom.lat. range: 23°?52° S, were digitally scanned at 5-min intervals at nighttime 18:00?06:00 LT for 13 months January 2004?January 2005. An important parameter of the F-region, so-called range spread-F Sr, was for the first time quantified in km. Maximum in Sr was recorded at a sounding frequency of 1.8 MHz for each night and for each ionosonde station. A distinct pattern in the magnitude in km and in the percentage occurrence of the range spread-F was present in southern winter only the June solstice. The sub-auroral region geom. lat. ?52° S is characterised by consistently high spread-F average Sr?100 km on 80?100 per cent of the observed nights. There is a sharp equatorward boundary in the spread-F activity in a latitudinal range: 52°?48° S followed by a midlatitude region 44°?48° S which exhibits a peak in Sr ?50 km in winter only, observed on half of the nights. The midlatitude activity reaches its minimum at 42°?43° S, with Sr less than 20 km on one third of the nights. The low midlatitudes 23°?36° S are characterised by a strong peak in Sr again in winter, centred at about 30° S average Sr?70 km on 80 per cent of the nights. The pattern becomes largely absent during other seasons particularly in southern summer the December solstice when spread-F activity shifts to sub-auroral latitudes. The pattern in the occurrence of spread-F appears to have a global character as the enhanced spread-F activity is observed in the Japanese sector in local summer i.e. the June solstice. It appears that the midlatitude spread-F minimum is only apparent but not real. It delineates the boundary between aurorally generated spread-F due to travelling ionospheric disturbances, TIDs and low midlatitude spread-F whose origin is not known.





Author: L. A. Hajkowicz -

Source: https://hal.archives-ouvertes.fr/



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