Dynamical implications of Si iv line profiles from OSO-8 observations

The widths and rms variations of line centers for 1393 profiles from the Si iv ion in the solar transition zone, as observed by OSO-8, are analyzed to give the amplitudes and periods of three postulated types of disturbance: sinusoidal acoustic waves; sinusoidal acoustic shocks; and normally propagated MHD waves. All three assumptions lead to mean intervals between disturbances of 40–50 s, but acoustic waves and shocks are rules out because they predict intensifications of brightness far in excess of anything observed. MHD disturbances in magnetic fields 2 G are consistent with observations, but normally propagated disturbances also give too great an intensification in brightness. Disturbances with wave vectors at an angle to the magnetic field are suggested.