Expositora: Anna Krupka (Centre for mathematical Plasma Astrophysics, Department of Mathematics, Katholic University of Leuven)
Fecha: viernes 16 de octubre, 11:30 hs.
Resumen: Magnetohydrodynamic waves and discontinuities are usually treated as distinct problems: waves are described in terms of propagating modes, while shocks and other discontinuities are characterised by jump conditions between two plasma states. A wave-aligned formulation based on Q-variables describes both within the same framework.
Q-variables describe plasma in terms of waves by combining velocity and magnetic field into a single variable. They can decompose plasma into MHD waves and their propagation directions. The classical Rankine-Hugoniot conditions derived in Q-variables reveal the wave structure contained in the jump relations while remaining fully equivalent to the standard MHD description.
This formulation also provides a natural basis for classifying ideal-MHD discontinuities. Contact, tangential and rotational discontinuities, as well as different shock families, show characteristic signatures in Q-space that can be expressed through relations between wave-aligned variables on either side of the discontinuity.
These analytical results can then be extended into a diagnostic framework by mapping Q-variables across discontinuities and using the resulting relations to identify the structure in numerical simulations and, ultimately, plasma observations. The broader goal is to develop a common language in which MHD waves, their propagation directions and the discontinuities connecting different plasma states can all be analysed within the same formalism.
