Previous works (e.g., Nykyri+, 2012; Nykyri+2019; Burkholder+2020,2021) have shown that magnetic reconnection can create large-scale diamagnetic cavities in high-latitude magnetosphere where particles can be accelerated to 100s of keV in reconnection quasi-potential. The acceleration mechanism creates strongly perpendicular pitch angle distributions for ions and electrons, likely contributing to the source of the ion temperature anisotropy in high-latitude magnetosphere. Recently, 4 MMS spacecraft flew through dusk-sector southern hemispheric diamagnetic cavity observing strong ULF wave activity, driven by the drift-mirror instability, at the edge of the cavity. The high-energy electrons within these wave field depressions showed counter-streaming pitch angle distributions while ions remained trapped (Nykyri+, 2021, GRL). The Pc5 range ULF waves also contained strong higher frequency plasma wave activity. In this talk we use information theory (mutual information and transfer entropy) and show that energetic electrons during this event indeed originate from diamagnetic cavity and are scattered into the loss cone likely by the oxygen cyclotron waves found inside mirror-mode waves
