Observation of upper extent of Ionospheric Alfven Resonator frequencies at low latitudes

Abstract

High frequency magnetic data have been analyzed at low latitude Indian stations to study the occurrence and behavior of Ionospheric Alfven Resonator (IAR). IARs are observed in the dynamic spectrum of magnetic variations in the form of spectral resonance structures (SRS). The current investigation aims to study the behavior of IAR resonance frequencies with respect to the solar activity. For this purpose, we analyzed the data of induction coil magnetometer for the years 2012-2014 which were in the ascending phase and maximum of solar cycle 24 and the year 2018 which was close to solar minimum. The analysis exhibited that the number of harmonics of IARs observed is less as the solar activity increases and more harmonics are observed when the solar activity decreases. We scanned for the IAR events where the resonance frequencies reach as high as the fundamental frequency of Schumann resonance and it is revealed that such events occur more frequently in the 2018 as compared to the years 2012-2014. Relation with ionospheric parameters are deduced.