Solitary kinetic Alfvén waves: A study of the Poynting flux

Using a particular mode of the FREJA wave experiment (three magnetic and one electric simultaneous measurements), we have investigated the electromagnetic structure of the solitary kinetic Alfven waves observed in the topside ionosphere. It is shown that these strong electromagnetic spikes (ΔE ≈ 100 mV/m and ΔB ≈ 10 nT) have mainly a rotational character with, nevertheless, a tiny compressional component (ΔB‖/ΔB ≈ 10 %). They seem to be associated with small-scale (100 m) tubular current structures. On the assumption that their electric component is perpendicular to the magnetic one their Poynting flux is estimated. Values of the order of 10−3 W/m2 are measured.