Survey of Equatorial Fast Magnetosonic Waves Observed by RBSP

A statistical survey of equatorial magnetosonic (MS) wave properties and spatial distribution, as a function of geomagnetic activity, is performed using the wave magnetic field data from Van Allen Probes over the 43 months. Our global survey shows that strong amplitudes and high occurrence of MS waves are generally observed near the equator, outside the plasmapause, on the dawnside during geomagnetically disturbed periods. Outside the plasmapause the statistical frequency distribution of magnetosonic waves follows the variation of the lower hybrid resonance (LHR) frequency, but this trend is not clearly observed inside the plasmasphere or plasma boundary layer. There are two high occurrence rate belts in wave frequency spectrum outside the plasmapause: the higher one, with 0.7 LHR frequency, is mainly observed L>3.5 and consistent with a high electric intensity belt at frequency spectrum, while the other, with 0.2 LHR frequency, is mainly observed L<5 during geomagnetically disturbed periods when energy ratio of ion ring current and Alfven wave is 2 10, but without an electric intensity belt company. Our normal angle survey suggests that the central frequency waves with same L and frequency follows a nearly Gaussian distribution, and the standard deviation shows its peak at outside plasmaplause, following the LHR frequency.