Instantaneous maps of the European middle and high-latitude ionosphere for Hf propagation assessments

Instantaneous mapping techniques applied to geographically irregularly spaced foF2 measurements can lead sometimes to non-physical gradients. A procedure is presented to avoid such problems by the use of screen points within the area of interest having values derived from single station models (SSM's). Spatial smoothing uses the kriging method in terms of the deviations between the measurements and corresponding figures given by the adopted long-term mapping method of COST 238 (PRIME). A new first-order trough model is introduced as a correction to the mapped values on the equatorial side of the auroral oval by night. Sample maps of the European ionosphere generated by this technique are compared with internationally recommended monthly median prediction maps to demonstrate the lack of spatial structure these latter give, with consequential errors when applied to propagation assessments. The use of the new maps, particularly for the higher latitudes, is advocated. (C) 1998 COSPAR. Published by Elsevier Science Ltd.