Effects of Dayside Shear Flows on the Excitation of Waves in the Magnetosphere

Abstract:

We present how wave occurrences in the magnetosphere can be affected and driven by dayside shear flows. It is found that the solar wind plays a crucial role in providing free energy to magnetospheric wave activities. By adopting both analytical and numerical dipole models, we show that inhomogeneous shear flows in the magnetosheath, which depends on the solar wind speed, are responsible for the excitation of the Doppler-shifted waves in the outer edge of magnetosphere. For instance, high frequency component, which is comparable to EMIC band, is consistently excited by the averaged shear flow variations in the magnetosheath. Our results are found to be very consistent with the observational feature of current statistical studies such that dominant occurrences are found at the outer shells, and that there is strong asymmetric distribution between dawn and dusk.