Asymmetric Distributions of Auroral Kilometric Radiation in Earth's Northern and Southern Hemispheres Observed by the Arase Satellite

Auroral kilometric radiation (AKR) is generated at high latitudes and can propagate down to low latitudes. Due to the lack of direct observations, the characteristics of AKR in the middle and low latitudes of two hemispheres have not been studied so far. Here, using observations of the Arase satellite from 23 March 2017 to 31 July 2019, we present the first statistical study of AKR distribution in the northern (Magnetic latitude Mlat = 0 degrees-40 degrees) and southern (Mlat = -40 degrees-0 degrees) hemispheres. Results (totally 30,353 samples) show that relatively high occurrence rates (>30%) of AKR in the northern (southern) hemisphere primarily stay in the region of magnetic local time MLT = 17-24 (MLT = 21-05). About 60% of wave samples in the northern (southern) hemisphere are observed in the frequency range of <= 300 kHz (>300 kHz). The asymmetric distribution in two hemispheres can further enrich our understanding of AKR.