Prof Róbert von Fáy-Siebenbürgen
This site contains: Solar Physics | Space Weather/Space Plasma Physics | Computational Magnetohydrodynamics (CMHD) | Helioseismology | Stability of MHD shear flows
Studies of linear and nonlinear resonant MHD wave heating under
solar atmospheric conditions.
Studies of nano-scale reconnection MHD heating under solar
Space Weather/Space Plasma Physics
Studies of resonant flow instabilities in MHD involve the generalisation
of stability theory when resonance occurs in a steady plasma. This theory has been
extended to dilute plasmas, which more realistically describes the magnetosphere,
heliosphere or space weather.
Computational Magnetohydrodynamics (CMHD)
Modelling of explosive events (EEs), blinkers, nano-flares and solar
tornadoes. EEs, blinkers and nano-flares are the smallest scale phenomena observable
with the latest very high-resolution satellite techniques and are believed to be the
basic building blocks of atmospheric heating. My joint ground-based (Tenerife) and
satellite (SOHO, Yohkoh, TRACE) observation campaign was one out of the very few
European projects supported by ESA/NASA SOHO Science Planning (11/1998).
Helioseismology provides one of the most precise measurements in astronomy
and yields information about the internal structure of the Sun. Since there is a
significant discrepancy between theoretical predictions and satellite measurements I am
re-visiting the models of solar internal f/p/g-modes to include the combined
effects of an atmospheric magnetic field, temperature and steady state changes
during a solar cycle.
Stability of MHD shear flows
Stability of open shear flows is of fundamental importance in geophysics
and astrophysics. Examples of such flows include plasma flows in the vicinity of the
magnetopauses of the Earth and planets, the boundaries between fast and slow streams of
the solar wind, the flow in the vicinity of the heliopause, flows in the interaction
regions of colliding stellar winds in binary stellar systems, and astrophysical jets.
To study the stability of a shear flow with respect to perturbations finite in space we
have to solve an initial-value problem. Then two scenarios are possible. In the
first scenario the initial finite perturbation exponentially grows at any spatial position.
Such a type of instability is called absolute. In the second scenario the initial
perturbation also grows exponentially, but it is swept away by the flow from any finite
region so fast that it decays at any fixed spatial position. Such a type of instability is
called convective. The classification of absolute and convective instability is important
for the understanding of the physical processes in geophysical and astrophysical plasmas,
and for the interpretation of new satellite (SOHO, TRACE, RHESSI) observational data. In
spite of it fundamental importance there is little attention paid to this problem in MHD.
Maintaned by Marianna Keray