Numerical Simulations of Trapped Slow Magnetosonic Waves in Solar Coronal Plumes

Abstract

Recent observations of polar plumes in the southern solar coronal hole by the Extreme ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft show signatures of quasi-periodic compressional waves. Here, we present the results of a nonlinear, 2D MHD simulation of the slow magnetosonic waves in plumes for typical coronal conditions consistent with observations. Our numerical simulations confirm the interpretation of the observed intensity fluctuations as propagating slow magnetosonic waves. On March 7 1996 DeForest and Gurman (1998) detected quasi-periodic intensity variations of 10-20% in the EIT Fe IX and X line emission at 171A&ring that propagate outward in several polar plumes at 75-150 km s^-1 with a period of 10-15 minutes. The observed propagation velocity agrees well with the expected sound velocity inside the plumes. The lower phase speed in the plumes than in the ambient plasma leads to partial trapping of the slow magnetosonic waves in the plumes. The slow magnetosonic waves may contribute to the heating of the lower corona by compressive dissipation