The spatial features of the up- and downshifted maxima in stimulated electromagnetic emissions

The determination of the source regions of some of the spectral components of stimulated electromagnetic radio emissions (SEE) is reported. The investigation was performed using observations made in 2005 during heating campaigns with the EISCAT heating facility near Tromsø, Norway. A four-channel high-frequency interferometer, designed by the Polar Geophysical Institute (PGI), was used to determine the arrival direction of the SEE signal. Three channels of the interferometer were connected to three antennas of the receiving antenna array. The antennas were installed in the meridional (north-south) and zonal (east-west) planes. The distance between the heating facility and receiver antenna array was 12.6 km. The measurements allowed determination of the azimuth and elevation angles of the intensity-weighted mean location of the SEE source regions by the phase difference method. In order to increase accuracy and eliminate the effects of interferences, data were selected based on the coherence of the signals. The results show that different parts of the down- and up-shifted maxima (DM, UM) features in the SEE spectrum are generated in different regions of the ionosphere, possibly in an elongated region along the magnetic field.