First results of artificial stimulation of the ionospheric Alfvén resonator at 78°N

On 2 December 2005 a modulated X-mode ionospheric modification experiment was carried out using the Space Plasma Exploration by Active Radar (SPEAR) high power facility on Svalbard (78.15°N, 16.05°E), with the intention of artificially stimulating the Ionospheric Alfvén Resonator (IAR). A modulation frequency of 3 Hz was superimposed on a 20 minute on/off cycle. Local ionograms showed an E region ionosphere of sufficient plasma density for the SPEAR beam to strongly interact with the low-altitude ionospheric plasma. The Barentsburg pulsation magnetometer monitored the resulting wave activity in the 0.5–5 Hz frequency range. Clear enhancements of the spectral power at 3 Hz were observed in the D component data, when SPEAR was transmitting and there was little natural Pc1 wave activity. During part of the interval, when high power substorm-associated Pc1 waves occurred, the polarisation of the artificially-stimulated wave rotated from the D to the H component.