Numerical simulations in astrophysical context: I. MHD instabilities; II. The model of aspherical dust dynamics for interpretation of the GIADA in-situ measurements in the coma of 67P/C-G
Abstract
I. Review of some results from numerical simulations of the following models will be presented:
A new Riemann-solver-free CWENO approach, named, conservative-primitive variables
strategy (CPVS) for numerical resolving sharp discontinuities and very strong shocks has
been developed. Its high accuracy and speed have been tested against 1D relativistic
hydrodynamics and compared with the operator splitting approach.
Two groups of 3D simulations of (M)HD instabilities were adopted with operator-splitting
ideal MHD ZEUS-MP/2 code. The first results shows the conditions under which the Tayler
instability is suppressed in dependence on the strength of poloidal field in a coupled toroidalpoloidal
magnetic configuration. The second group of simulations studies the onset, the timeevolution
and the characteristics of Rayleigh-Taylor instability in the collision between two
plasma plumes.
A new numerical scheme of solving 2D+t MHD equations for incompressible viscous and
conductive flow has been used for simulating coupled Kelvin Helmholtz and tearing mode
instability in the magnetopause boundary layer model. Such modeling of the magnetopause
response to the incoming solar wind is likely to permit more realistic interpretation of the
transient events, registered by ground-based magnetometers.
In order to model the magnetoconvection in sunspots the transition from 3D to 2D turbulence
under the influence of strong magnetic fields is simulated. The obtained results (with
NIRVANA code) show that turbulence intensities and magnetic energy exhibit strong
quenching behavior.
II. In order to prepare the interpretation of the GIADA in-situ data of Comet 67P/ Churyumov-
Gerasimenko a model of dust dynamics is indispensable. The currently used 3D+t model assumes
sphericity of the grains. We report the first steps in developing of the model of aspherical dust grain
dynamics in the cometary atmosphere. On this stage we study the grain motion in aerodynamic
force free region. The grains are convex polygonal bodies. In addition, a new approach for resolving
the inverse problem is discussed, namely, based on GIADA observations, we could determine the
probable location of the particles emission on the nucleus.
