资源环境科技发展态势分析平台

Observations of magnetospheric chorus being triggered by lightning-induced whistlers are rare but provide a unique opportunity to remotely diagnose wave-particle interactions in the Earth's radiation belts. The observations presented herein are unique in that whistlers, originating from lightning, are seen to trigger upper band chorus repeatedly over the course of 2hr. Each whistler exhibits a distinct upper frequency cutoff that is used to estimate the anisotropy of the hot plasma distribution. Resulting anisotropy estimates are in good agreement with previous in situ measurements. While the anisotropy determines wave growth in the linear regime, access to the nonlinear regime requires the in situ wave amplitude to exceed the threshold for phase trapping of energetic electrons. The results suggest that while upper band chorus is less favorable to be spontaneously generated, the conditions in this band are more conducive for triggering of the chorus instability by an external input wave.

Plain Language Summary The near-Earth space environment is in a plasma state and is also extremely variable due to the solar-driven phenomena and rich physical interactions between various layers of the upper atmosphere. This region hosts a large number of electromagnetic wave modes, which interact with high-energy particles that form the Earth's radiation belts. The state of the radiation belts affects communication and electrical power technologies in space and on Earth. Despite many years of investigation many fundamental properties of the near-Earth space environment remain poorly quantified. We report observation of the interaction of waves from atmospheric lightning with radiation belt particles. The observation provides a unique opportunity to remotely sense the dynamics of the energetic particle population in the Earth's radiation belts and how this population leads to amplification and generation of waves.