[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P10] On the EMIC wave activity in the inner magnetosphere associated with solar wind dynamic pressure variations

*Shreedevi Porunakatu Radhakrishna¹, Yoshizumi Miyoshi¹, Yiqun Yu², Tian Xingbin², Vania Jordanova³, Chae-woo Jun¹, Kazuo Shiokawa¹, Masafumi Shoji¹, Satoko Nakamura¹ (1.Institute for Space-Earth Environmental Research (ISEE) Nagoya University Nagoya Japan, 2.School of Space and Environment, Beihang University, Beijing, China, 3.Los Alamos National Laboratory, Los Alamos, NM, United States)

Keywords:Wave-particle interaction, EMIC waves, Dayside magnetopsheric compressions

Electro Magnetic Ion Cyclotron (EMIC) waves are known to occur naturally from the temperature anisotropy of protons. The two main driving mechanisms for the EMIC wave excitation are injection of energetic protons into the night side inner magnetosphere from the tail plasmasheet and the magnetospheric compressions associated with the solar wind dynamic pressure enhancements at the dayside. We have better understanding of the origin and distribution of EMIC waves associated with storm time hot ion enhancements in the ring current region as it has been a subject of many investigations. However, the mechanisms leading to the excitation of EMIC waves in the dayside inner magnetosphere owing to enhancement in the solar wind dynamic pressure is not clear. In this study, we combine the satellite/ground based observations along with global modeling to understand the EMIC wave generation in the inner magnetosphere in response to solar wind dynamic pressure enhancements. The EMIC wave events triggered by solar wind pressure enhancements are identified using the RBSP satellite measurements and ground magnetic field measurements. In order to understand if the magnetic field enhancements in the dayside inner magnetosphere lead to increase in temperature anisotropy thereby generating EMIC waves, we conducted a simulation of the EMIC wave-particle interaction using the SWMF (BATSRUS+RAM-SCBE) model. The results show that during periods of enhanced solar wind dynamic pressure, the temperature anisotropy of protons increases at the dayside inner magnetosphere through the compression of the magnetosphere. The simulated EMIC wave growth rates enhanced in regions of higher temperature anisotropy in the dayside inner magnetosphere. The ground magnetometers also recorded the presence of Pc1/EMIC waves at these regions. Our investigation will analyze in detail the physical mechanisms that lead to the excitation of EMIC waves in the dayside inner magnetosphere during periods of enhanced solar wind dynamic pressure.