Asymmetry of Auroral Kilometric Radiation in the Northern and Southern hemispheres

Auroral kilometric radiations (AKR) are existed by suprathermal (1-10keV) electrons, which are accelerated by parallel electric fields and pitch angle scattered by magnetic field gradients. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study of AKR distribution characteristic in the region of λ = 0°−40°and L = 3.0−9.0. Results (totally 32,043 samples) show that southern AKR on the nightside (12,853 samples) are positioned to the east relative to their northern conjugates (13,630 samples), the wave frequencies and amplitudes of AKR in the southern hemisphere are greater than those in the northern hemisphere. Further studies suggest that SYM-H indexes and interplanetary magnetic field (IMF) have different distributions in the northern and southern hemispheres. The probable reason is that different IMF conditions cause asymmetric Field-aligned currents between the northern and southern hemispheres, then yield the asymmetry of AKR and auroras. This study helps to provide more information on the magnetosphere-ionosphere-atmosphere coupling.