OSCILLATIONS OF MHD SHOCK WAVES ON THE SURFACES OF TTAURI STARS Authors: A.V. Koldoba, G.V. Ustyugova, M.M. Romanova and R. V. E. Lovelace [return] 
Sketch of the geometry of the flow. Matter with density r_{in } and pressure p_{in} flows towards the star with velocity vin along the magnetic field which has strength Bin and is inclined relative to the normal to the surface of the star x at an angle. Matter slows down in the MHD shock wave close to the surface of the star and radiates and cools down in the “cooling zone”. Matter may have different angle relative to the field, but we consider the coordinate system in which vectors velocity and magnetic field are parallel to each other. 

Time dependence of the shock front coordinate x_{s} (top panel) and luminosity J (bottom panel) for case I (“real” cooling function, v_{in} cos = 1.3 10^{7}cm s^{−1}). The shock front coordinate is in units D, luminosity in units of J_{in}, and time is in seconds.


Time dependence of shock front coordinate x_{s} (top panel) and luminosity J (bottom panel) for case II (powerlaw cooling function, v_{in}cos = 1.3 10^{7}cm s^{−1}). The coordinate of the shock front x_{s} is in units D , the luminosity is in units of J_{in}, and the time is in seconds.


Distribution of different parameters along the x−axis: velocity component along the field lines (top panel), density and temperature (middle panel) magnetic field and plasma parameter b (low panel). All variables are shown in dimensionless form. In the incoming flow v_{x} = −1, r = 1, T = 0 (almost zero), B_{x} = 0.48, B_{y} = 0.076. Matter inflows from the right boundary, a star is at the left. 

The position of the boundary between stable and unstable radiative shock waves as a function of parameters (X, sin ) for a velocity of accretion vin cos = 1.3 10^{7}cm s^{−1}. 

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