Spatial dependence of banded chorus intensity near the magnetic equator

Abstract

Data from 12 different Cluster orbits containing banded chorus emissions, with observations from 22 different events spread across the four Cluster spacecraft, are used to show the spatial dependence of banded chorus intensity near the magnetic equator under conditions of moderate magnetic disturbance (Kp ≤ 5). The intensities for upper band (UB) and lower band (LB) chorus were manually determined from frequency-time spectrograms generated from WBD data. Out of the 22 events, 5 of the spacecraft observations showed a complete absence of chorus emissions within 0.5° of the magnetic equator. The intensity, I, of the chorus emissions generally increased exponentially with distance, z, away from the magnetic equator according to the relation I = Ioeaz, where α is the spatial growth factor. The exponential distribution of α provides a new boundary condition for consideration in current and future chorus generation models. © 2012. American Geophysical Union. All Rights Reserved.