SOLITARY KINETIC ALFVEN WAVES - A STUDY OF THE POYNTING FLUX

Using a particular mode of the FREJA wave experiment (three magnetic a nd one electric simultaneous measurements), we have investigated the e lectromagnetic structure of the solitary kinetic Alfven waves observed in the topside ionosphere, It is shown that these strong electromagne tic spikes (Delta E approximate to 100 mV/m and Delta B approximate to x 10 nT) have mainly a rotational character with, nevertheless, a tin y compressional component (Delta B-parallel to/Delta B approximate to 10 %), They seem to be associated with small-scale (100 m) tubular cur rent structures. On the assumption that their electric component is pe rpendicular to the magnetic one their Poynting flux is estimated, Valu es of the order of 10(-3) W/m(2) are measured.