Ionospheric spread-F occurence associated with tropospheric atmospheric gravity waves

Abstract

Ground-level atmospheric gravity waves (GL-AGWs) recorded at Brisbane (Australia) from 1963 to 1966 using microbarographs have been investigated for possible associations with ionospheric spread-F at certain locations, particularly those with longitudes not displaced significantly from the longitude of Brisbane. Of the 121 well-defined events identified, 54 were found to be associated with tropospheric cold fronts which passed through Brisbane 1 day and particularly 2 days after these GL-AGWs were recorded. For the 67 non-frontal events some significant associations were found with spread-F recorded at some high mid-latitude stations situated at longitudes to the west of Brisbane in the northern hemisphere. No associations were found for stations (including Brisbane) close to the longitude of Brisbane. However the paper draws attention to and illustrates some of the results reported by Khan (A study of ionosphere structures with direction finding equipment, M Sc. thesis, The University of Queensland, Brisbane, Australia, 1973) which show that on some occasions for quiet conditions at Brisbane when travelling ionosphere disturbance (TID) wave amplitudes are so low that spread-F is not recorded, associations can be found between these TID wave oscilations and those at ground level recorded by microbarographs. No associations were recorded with spread-F for the events associated with the fronts