Seasonal Characteristic of Auroral Kilometric Radiation in the Radiation Belts

Auroral kilometric radiation (AKR) is one of the strong radio emission phenomenons with kilometer wavelengths, and similar emissions have been detected on other magnetized planets of the solar system. AKR is generated by suprathermal electrons (1-10 keV) injected from the plasma sheet and has been observed at the lower latitude region of the radiation belts from the Van Allen Probes. Here, we analyze the seasonal characteristic of AKR in the region of L = 3-7 and λ = 0^◦− 20^◦ using observations from 1 December 2012 to 31 November 2018. Statistical results (4,559 events in total) show that AKR emissions occur most frequently in autumn both in the northern and southern hemispheres. The correlation coefficient between the number of AKR events in each season and the Kp (the geomagnetic activity index) index of these events can reach 0.82. These results suggest that AKR emissions in the lower latitude regions depend on the geomagnetic activity.