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

摘要

Typical 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 (P-dyn) 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 P-dyn 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 P-dyn in magnetospheric plasma dynamics.