Enhanced Solar Wind Dynamic Pressure as a Driver of Low‐Energy Proton Temperature Anisotropies and High‐Frequency EMIC Waves

Abstract

AbstractTypical and high‐frequency electromagnetic ion cyclotron (EMIC) waves were simultaneously registered by satellites in the afternoon sector of the inner magnetosphere during enhanced solar wind dynamic pressure (Pdyn) on 3 November 2015. The compression of the dayside magnetosphere leads to amplified field intensities and squeezed field lines, which causes adiabatic accelerations of both hot (10s keV) and low‐energy (10s–100s eV) protons at the equatorial region. Temperature anisotropies of low‐energy protons enhance in immediate response to Pdyn impact accompanied by the generation of EMIC waves with frequencies close to proton gyrofrequencies. The low‐energy protons with enhanced fluxes are found to resonate with the high‐frequency EMIC waves, indicating their potential contributions to wave excitation. The comprehensive analysis of this work provides a new physical scenario describing the evolution of low‐energy protons and the generation of high‐frequency EMIC waves, reflecting the critical role of Pdyn in magnetospheric plasma dynamics.