Comparison of the Wave Structure of IAR Emission in the Mid-Latitude and Auroral Regions

We compare the properties and structure of ionospheric Alfvén resonator (IAR) emissions from simultaneous ground-based magnetic observations at mid and high latitudes. Data from three stations were used: two mid-latitude Mondy (MND) and Uzur (UZR) stations, and one high-latitude Istok (IST) station, located in the auroral zone. We found very significant differences between the wave structure at middle and high latitudes, although the spectral characteristics in these two regions are almost the same. We obtained information about the structure of standing Alfvén waves in the IAR from the ratios of harmonic frequencies. The frequency ratio uniquely determines the waveform of each harmonic. We found earlier that at middle latitudes, the frequencies of harmonics are proportional to the series of odd numbers 1:3:
$5\ldots $
This means that at the resonator lower boundary, which is presented by the Earth’s crust, an antinode of the magnetic field of the wave is steadily formed. At the high latitude of the auroral station, an uncertain situation arises: there are no definite stable relationships between the frequencies of the first three harmonics. Accordingly, the phase factor
$\Phi $
at medium latitudes is almost constant, hardly deviating from its mean value of −0.5, while in the auroral zone,
$\Phi $
does not have any specific meaning. It has been suggested that the strong horizontal heterogeneity of the high-latitude ionosphere and the limited transverse dimension of IAR wave structure are the reasons for the observed picture in the auroral region.