Spatial Distribution and Plasmaspheric Ducting of Auroral Kilometric Radiation Revealed by Wind, Polar, and Arase

Abstract

Auroral Kilometric Radiation (AKR), the dominant radio emission from Earth, has been extensively studied, though previous analyses were constrained by limited spacecraft coverage. This study utilizes long-term observations from Polar, Wind, and Arase spacecraft to generate comprehensive global AKR occurrence rate maps, revealing a high-latitude and nightside preference. A detailed investigation of the equatorial shadow region confirms that the dense plasmasphere blocks AKR emissions across all wave frequencies. Low-frequency emissions (<100 kHz) are presents outside the shadow region at larger radial distance, which is attributed to magnetosheath reflection, while higher-frequency emissions (>100 kHz) propagate via plasmaspheric ducting and leakage, filling the equatorial region immediately outside the plasmasphere. Ray-tracing simulations identify low-density ducts within the plasmasphere as crucial channels that enable AKR to penetrate the dense plasmasphere, particularly at higher frequencies. These results align with meridional AKR observations, offering new insights into AKR propagation patterns.