The ionospheric Alfvén resonator (IAR) can amplify and accumulate ultra-low frequency (ULF) wave energy in the upper ionosphere. Close connection of the IAR emission features with state of the ionosphere motivates many authors to study the details of this con- nection, and make suggestions about how to use observations of the spectral structure of the electromagnetic background in the range of 0.5–10 Hz for sounding ionospheric parameters and clarifying ionospheric models. In this paper we propose a new approach to analysis of emission of ionospheric Alfvén resonator (IAR). We apply the IRI-2012 version of International Reference Ionosphere model to calculate difference between frequencies of adjacent harmonics of IAR emis- sion. The calculated values are compared with the frequency data obtained from the search-coil magnetometer observations made at two different stations, the mid-latitude observatory Mondy (Eastern Sayan, Russia) and the high-latitude Sodankylä Geophysical Observatory (Finland). The results showed a good correlation between the measured and calculated values both at medium and high latitude. The calculation results at Mondy have a systematic error of about 0.35 Hz. The reasons of this discrepancy are discussed.