Abrupt Disappearance of Plasmaspheric Hiss inside the Magnetic Dip

Plasmaspheric hiss plays an important role in radiation belt electron dynamics, and its excitation and propagation have long attracted attention. During a substorm, Van Allen Probe B observed the disappearance of plasmaspheric hiss at the magnetic dip, which was driven by the injection of energetic protons. The perpendicular (to the magnetic field) components of both the wave vector and Poynting vector were directed radially outward. We analyzed the event from two perspectives: excitation and propagation. The growth rate of plasmaspheric hiss remained below the threshold both inside and outside the dip, indicating that the waves were not locally excited. Regarding propagation, theoretical calculations suggest that the observed whistler-mode hiss waves were reflected by the magnetic dip in a broad frequency range. Our results indicate the important role that the magnetic structures play in the propagation of plasmaspheric hiss.