Multi-spacecraft observations

Utilizing simultaneous twin Van Allen Probes observations of whistler mode waves at variable separations, we are able to distinguish the temporal variations from spatial variations, determine the coherence spatial scale, and suggest the possible mechanism of wave modulation. We report coherent whistler mode waves observed both inside and outside the plasmapause by two Van Allen Probes with a very large separation up to 4.3 Earth Radii. The source of the modulation are possibly associated with ULF waves as well as whistler mode wave propagation.

Reference: Li et al., (2017), Coherently modulated whistler mode waves simultaneously observed over unexpectedly large spatial scale, Journal of Geophysical Research: Space Physics, https://doi.org/10.1002/2016JA023706

We reported an new morphology of  magnetosonic waves which consisting of two bands of interleaved periodic rising-tone spectra observed by the Van Allen Probes, the THEMIS and MMS missions. We name them as “zipper-like” magnetosonic waves. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. A statistical survey based on 3.5 years of multi-satellite observations shows that zipper-like magnetosonic waves mainly occur on the dawnside to noonside, in a frequency range between 10 proton gyro-frequency and lower hybrid frequency. The zipper-like magnetosonic waves may provide a new clue to nonlinear excitation or modulation process, while its cause still remains to be fully understood.

Reference: Li et al., (2017), “Zipper-Like” Periodic Magnetosonic Waves: Van Allen Probes, THEMIS, and Magnetospheric Multiscale Observations, Journal of Geophysical Research: Space Physics,  https://doi.org/10.1002/2016JA023536