Abstrakt
Statistical analyses of Polar plasma wave data are performed to determine the occurrence frequency, intensity, and Poynting direction of similar to 360 Hz to similar to 1.8 kHz extremely low-frequency (ELF) electromagnetic waves (chorus, magnetosonic mode, and hiss) in the dayside sector of the magnetosphere. The study is limited to an L* range of 2 to 9 and a magnetic local time (MLT) range of 0900 to 1500, a region infrequently covered in past statistical surveys.
The study was performed on 1996-1997 data, an interval near solar minimum. It is determined that in the outer region of the magnetosphere, from L* = 6 to 9, the similar to 360 to similar to 800 Hz waves at Polar altitudes are typically characterized by downward (toward Earth) propagation.
The downgoing waves have been previously identified as chorus in Tsurutani et al. (2011). The downgoing chorus have intensities of similar to 10(-2) nT(2), are right-hand circularly polarized and are propagating close to parallel to the ambient magnetic field B-0.
The high rate of occurrence of these downward propagating waves narrows to a smaller region of L* = 6 to 7 for similar to 1.2 kHz waves.