The Generation of Coronal Loop Waves below the Photosphere by p-Mode Forcing

Abstract

Recent observations of coronal-loop waves by TRACE and within the corona as a whole by CoMP clearly indicate that the dominant oscillation period is 5 minutes, thus implicating the solar p modes as a possible source. We investigate the generation of tube waves within the solar convection zone by the buffeting of p modes. The tube waves--in the form of longitudinal sausage waves and transverse kink waves--are generated on the many magnetic fibrils that lace the convection zone and pierce the solar photosphere. Once generated by p-mode forcing, the tube waves freely propagate up and down the tubes, since the tubes act like light fibers and form a waveguide for these magnetosonic waves. Those waves that propagate upward pass through the photosphere and enter the upper atmosphere where they can be measured as loop oscillations and other forms of propagating coronal waves. We treat the magnetic fibrils as vertically aligned, thin flux tubes and compute the energy flux of tube waves that can generated and driven into the upper atmosphere. We find that a flux in excess of 10^5 ergs/cm^2/s can be produced, easily supplying enough wave energy to explain the observations. Furthermore, we compute the associated damping rate of the driving p modes and find that the damping is significant compared to observed line widths only for the lowest order p modes.