Diurnal behaviour of the ionospheric Alfvén resonator signatures as observed at high latitude observatory Barentsburg (L=15)

Abstract. The signature of the ionospheric Alfvén resonator (IAR), so called spectral resonant structures (SRS) in the spectra of the electromagnetic noise in the range of 0.1–10 Hz is rather frequently observed with the search coil magnetometer at observatory Barentsburg on Svalbard (L=15). In this report we discuss some peculiarities of diurnal occurrence of SRS at this high latitude station. We show that the pronounced minimum of the SRS occurrence around noon can not be explained by the diurnal variations of the solar zenith angle (illumination of ionosphere). We conclude that the SRS occurrence minimum is the result of the enhanced variability of ionospheric parameters when the observing point enters (during the Earth's rotation) the region of the ionospheric projection of the dayside cusp and its vicinity.