Interplay of Kelvin Helmholtz (KH) and Tearing mode Instability during High Speed Stream (HSS) Events

We study the interaction of KHI and tearing mode instability during High Speed Stream events. We use multiple satellite data and global MHD models to analyze this interaction. It is well known that KHI is instigated for shear velocity greater than local Alfven velocity. This condition is met on the flanks of the magnetosphere where the shocked Solar wind speeds up from sub to super Alfvenic velocities. Thus the instability grows using the free energy available in the shear flow. An interesting result is that this instability is relaxed by magnetic field tension. Tearing mode instability on the other hand is a resistive instability, uses the free energy available in the sheared magnetic fields to grow. During HSS events, these two instabilities together are accounted for transferring mass and momentum into the magnetosphere. Long duration (~ days) HSS speeds are ideal for the development of the KHI and the Alfvenic fluctuations in the IMF Bz are responsible for Flux transfer events (FTE). The goal of this study will be to study these two instablities at work together and how they counteract each others effect.