## 2. The equilibrium configurationWe consider a static 1D planar equilibrium model composed of two
semi-infinite uniform plasma layers which embrace a nonuniform plasma
layer. We use a system of Cartesian coordinates with the The magnetic field is assumed to be constant in the whole space and is oriented along the axis: . Gravity is neglected in the present analysis. Since the magnetic pressure is constant, the thermal pressure is also constant and so is the plasma parameter : In addition we can freely specify either the temperature or the density . Of course, implies that The object of the present paper is to study the absorption of slow and fast magnetosonic waves by coupling to local resonant slow magnetosonic waves. The resonant slow waves are controlled by the local cusp frequency which is determined by the wave vector and the local cusp speed. Hence in the present context it is convenient to prescribe the variation of the square of the local cusp velocity as a function that is monotonous inside the nonuniform layer and is constant elsewhere: The expressions for density, local Alfvén speed and local sound speed take the simple forms: where is prescribed by Eqs (3). The dimensionless Alfvén, sound, and
cusp speed as functions of coordinate
We use this model for studying the resonant absorption of
magnetosonic waves in different structures in the solar atmosphere.
The incoming wave is launched from the lower uniform layer
with a prescribed frequency
and a prescribed wave vector
, and propagates towards the nonuniform layer.
At the boundary the wave is partly reflected and
partly transmitted. The energy of the transmitted wave is partly
absorbed in the nonuniform plasma due to the resonant excitation of
local waves. With our choice of the direction of the © European Southern Observatory (ESO) 1997 Online publication: April 8, 1998 |