IAR Spectrograms

The spectrogram dataset contains the diurnal dynamic IAR spectra recorded at the mid-latitude Mondy station (51.6 N, 100.9 E) for 132 days in different years of the 24th solar cycle (2009–2019). IAR emission spectrograms are a fan-shaped set of bands, the frequency of which varies during the day. Each of the bands corresponds to one of the harmonics of the resonator emission. The width of the bands, i.e., their blurring, which reflects the quality factor of the resonator, also changes. The emission range is from tenths of a hertz to ~8 Hz — the frequency of the first harmonic of the Schumann resonance. The emission amplitude is small, it does not exceed a few pikotesla. In fact, we see the noise whose intensity is modulated by the resonator. Frequencies close to the IAR resonant frequencies stand out from the continuous background noise spectrum. The most commonly used device for recording ULF emissions of this type is an induction magnetometer. It consists of a multiturn coil with the core of an alloy having high magnetic permeability, a preamplifier, a set of filters, an analog to digital converter (ADC), and a digital storage. For precise timing, the device should be equipped with a receiver of signals from the global navigation satellite system (GPS and/or GLONASS). The spectrograms of this dataset have been obtained by processing records of the induction magnetometer LEMI-30. The IAR emission is visualized by constructing a spectrum of data from the output of the magnetometer. The most illustrative is the dynamic spectrum.
The other part of the dataset is the files Table_1.xls and README_File_for_Dataset.pdf with the results of processing the spectrograms, designed to obtain estimates of the frequencies of the IAR harmonics from the 1st to the 5th and their ratios for all 132 selected days.