Subject: What determines if a wave is reflected or absorbed?

If an electromagnetic wave is transmitted at 127MHz (roughly) from space, the 
permittivity of the plasma is 0 (and negative for frequencies below 127 MHz - 
quickly attenuating the signal). But there is nothing to mathematically 
indicate if the wave is reflected or the energy absorbed by the plasma. Is the 
signal reflected or absorbed and what determines this? Can it (determination of 
absorption or reflection) be mathematically modeled?

Re: What determines if a wave is reflected or absorbed?