Prompt Response of the Dayside Magnetosphere to Discrete Structures Within the Sheath Region of a Coronal Mass Ejection

A sequence of discrete solar wind structures within the sheath region of an interplanetary coronal mass ejection on November 6, 2015, caused a series of compressions and releases of the dayside magnetosphere. Each compression resulted in a brief adiabatic enhancement of ions (electrons) driving bursts of electromagnetic ion cyclotron (EMIC; whistler mode chorus) wave growth across the dayside magnetosphere. Fine‐structured rising tones were observed in the EMIC wave bursts, resulting in nonlinear scattering of relativistic electrons in the outer radiation belt. Multipoint observations allow us to study the spatial structure and evolution of these sheath structures as they propagate Earthward from L1 as well as the spatio‐temporal characteristics of the magnetospheric response. This event highlights the importance of fine‐scale solar wind structure, in particular within complex sheath regions, in driving dayside phenomena within the inner magnetosphere. On November 6, 2015, a sequence of abrupt changes in Earth’s magnetic field and the associated conditions in the solar wind were observed. Multispacecraft observations allow us to study both the spatial structure and evolution of the solar wind structures that impacted the Earth, as well as the response of Earth’s magnetic field and particles trapped within it. The fine‐scale structures observed in the solar wind are demonstrated to produce distinct magnetospheric particle distributions and wave excitation. This event highlights the importance of fine‐scale solar wind structure in driving magnetospheric phenomena. A sequence of discrete structures within an interplanetary coronal mass ejection sheath are tracked via multipoint measurementsEach structure results in magnetospheric compression, adiabatic enhancement of ions and electrons, and cyclotron wave growthThis event highlights the importance of fine‐scale solar wind structure and sheath regions for driving dayside magnetospheric phenomena A sequence of discrete structures within an interplanetary coronal mass ejection sheath are tracked via multipoint measurements Each structure results in magnetospheric compression, adiabatic enhancement of ions and electrons, and cyclotron wave growth This event highlights the importance of fine‐scale solar wind structure and sheath regions for driving dayside magnetospheric phenomena