Prompt Emergence and Disappearance of EMIC Waves Driven by the Sequentially Enhanced Solar Wind Dynamic Pressure
Zuxiang Xue, Zhigang Yuan, Xiongdong Yu
Abstract
Abstract Van Allen Probes (VAPs) and multiple ground‐based stations simultaneously observed prompt emergences and disappearances of electromagnetic ion cyclotron (EMIC) waves driven by the sequentially enhanced solar wind dynamic pressures in the dayside inner magnetosphere on November 6, 2015. The measured hot protons (>60 keV) display enhancements of perpendicular temperature during compressions, which provides sufficient temperature anisotropies for the EMIC wave generation so that the calculated linear growth rate also agrees well with the observed wave spectrum. There are bidirectionally propagating EMIC waves observed by VAPs at off‐equator regions (MLAT from ∼ 13° to ∼ 18°), which indicates local wave excitation under the compressions’ impact. The quick responses of waves and particle distributions to the compressions and decompressions at multiple points in the dayside suggest that the external pressure pulses can be a direct driver for the inner magnetospheric wave evolution and energetic particle dynamics.