LASP Magnetosphere Seminars

Abstract

The Kelvin-Helmholtz instability (KHI) is thought to be an important driver of activity in the earth’s magnetosphere. As the solar wind flows past the magnetospheric boundary, surface waves form that roll up into large vortices with scale sizes comparable to earth itself. An open question is exactly how the KHI can transfer mass, momentum, and energy from the solar wind into the magnetosphere. Three potentially important mechanisms for this coupling are magnetic reconnection, turbulence, and wave-particle interactions. On 8 September 2015, the NASA Magnetospheric Multiscale (MMS) mission observed the magnetopause over a prolonged period (~2 hours) when it was unstable to the KHI. Magnetic reconnection was confirmed on compressed current sheets on the edges of the vortices, known as “Type-I” reconnection. Additionally, turbulent cascades were observed within the vortices, often coinciding with the presence of enhanced electrostatic solitary wave (ESW) activity, and non-linear ion-acoustic waves. Now that MMS has been in operation for nearly a decade, more prolonged (>30 minute) KHI intervals have been identified, providing an opportunity to study these processes at different position along the earth’s magnetospheric flanks. This in turn will allow us to quantify them at different stages of the instability’s development. We show analysis of 13 such events, with a focus on the presence of Type I reconnection and ESWs. The importance of position along the flank and solar wind conditions are discussed, as well as the implications for Solar Wind-Magnetosphere coupling.