Kinetic Alfvén Waves in the Inner Magnetosphere Triggered by an Interplanetary Shock

An interplanetary shock impacted Earth's magnetic field on October 2, 2013, compressing the magnetosphere and triggering a global 3.5 mHz oscillation. This large-amplitude ULF (ultra low frequency) wave was observed in-situ, using both magnetic and electric field data, by the Van Allen Probe B spacecraft. At the same time, Van Allen Probe B observed higher frequency broadband wave power in conjunction with, and modulated by, this ULF wave. A detailed analysis reveals that these broadband waves are kinetic Alfvén waves, possibly generated by large-scale Alfvénic fluctuations coupling to smaller scales. This event suggests that magnetospheric compression by interplanetary shocks can induce abrupt generation of kinetic Alfvén waves over large portions of the inner magnetosphere, potentially resulting in prompt ion heating throughout the inner magnetosphere.