KU Leuven/CMPA seminar: Corrugation instability in partially ionised slow-mode shocks

KU Leuven Centre for mathematical Plasma-Astrophysics Seminar

Title: Corrugation instability in partially ionised slow-mode shocks

Speaker: Ben Snow from Exeter (UK) 

Abstract: A magnetohydrodynamic (MHD) shock front can be unstable to the corrugation instability, which causes a perturbed shock front to become increasingly corrugated with time. An ideal MHD parallel shock (where the velocity and magnetic fields are aligned) is unconditionally unstable to the corrugation instability, whereas the ideal hydrodynamic (HD) counterpart is unconditionally stable. For a partially ionised medium (for example the solar chromosphere), both hydrodynamic and magnetohydrodynamic species coexist and the stability of the system has not been studied. Here we present numerical simulations of the corrugation instability in two-fluid partially-ionised shock fronts that investigate the stability conditions, and compare the results to HD and MHD simulations. Our simulations consist of an initially steady 2D parallel shock encountering a localised upstream density perturbation. In MHD, this perturbation results in an unstable shock front and the corrugation grows with time. We find that for the two-fluid simulation, the neutral species can act to stabilise the shock front. A parameter study is performed to analyse the conditions under which the shock front is stable and unstable. We find that for very weakly coupled or very strongly coupled partially-ionised system the shock front is unstable, as the system tends towards MHD. However, for a finite coupling, we find that the neutrals can stabilise the shock front, and produce new features including shock channels in the neutral species. We compare the perturbation wavelength to the finite-width of the shock to comment on the stability of chromospheric slow-mode shocks.

​The seminar will be in a hybrid mode, in person in room 200B 00.07. The following (permanent) link may be used for online access:

https://eu.bbcollab.com/guest/7406a5ec00dc4ec6948200f9c769d454 

Date and time: Thursday, January 20, 2022 - 14:00 to 15:00

Date: 

Thursday, January 20, 2022 - 14:00 to 15:00
 

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