MHD Energy Flux in the Solar Wind

MHD waves are a characteristic feature of a magnetised plasma, illustrating the close connection in plasmas of electrodynamics and hydrodynamics. Magnetised plasmas, and thus also MHD waves, are rare on Earth but abundant in most of the rest of the universe. The current project aims at further developing the theoretical understanding of the energy flow associated with MHD waves in moving media.

The calculation of energy flux in MHD waves in a moving medium such as the solar wind requires care. The correct flux vector has been computed by Walker [Walker, A. D. M., Reflection and transmission at the boundary between two counterstreaming MHD plasmas - Active boundaries or negative energy waves? J. Plasma Phys., 63, 203-219, 2000].

The derived expressions do not include fluctuations in the plasma density. The reason for this is that it is assumed that the adiabatic law holds and so the plasma thermal pressure fluctuation acts as a proxy for the density fluctuation. The solar wind shows strong density fluctuations which may be easier to measure than the pressure fluctuations. This project will require the identification of suitable solar wind events for the ACE or WIND satellites and an evaluation of the best observations to use for most accurate computation of the flux vector. As a by-product it will test the validity of the adiabatic assumption. The first and final months will be spent at KTH, with three months at University of KwaZulu-Natal in-between.