Abstract Fast magnetosonic waves are electromagnetic waves with frequencies ranging from a few Hertz to several hundred Hertz, observed primarily near the magnetic equator. Recent studies demonstrate that magnetosonic waves can propagate into the L<2 $L< 2$ region, while their distributions and propagation properties there remain unclear. Using data from Van Allen Probes, we present the first systematic survey of magnetosonic waves’ spatial distribution in the L<2 $L< 2$ region, revealing important characteristics of their propagation and evolution. The frequency spectra of magnetic power spectral densities reveal that under disturbed geomagnetic conditions, the bandwidth of fast magnetosonic waves shifts to higher frequencies, and the spectra exhibit a radial inner boundary and a low‐frequency boundary, both of which depend on geomagnetic conditions. These findings advance our understanding of the propagation and evolution of magnetosonic waves in the L<2 $L< 2$ region and their potential role in the inner magnetosphere.
Observations from the Little Bunker
Last updated: November 30, 2025 04:25 AM
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