Propagating disturbances in the lower solar corona.

摘要

TRACE observations allow us to see propagating coronal waves in multiple narrowband filters and with high spatiotemporal resolution. I analyze four wave-front propagations observed in TRACE, in particular an event from 13 June 1998. Studying morphology and dynamics, I conclude observationally that three of the four fronts are fast-mode MHD waves.; Having developed new mapping algorithms, I automate the tracking of waves with bright fronts by finding reproducible fronts, natural trajectories, and fastmode velocities in large regions of the quiet corona. I use this automated method to examine the 13 June 1998 event in detail, and determine density and flux changes along several propagation tracks. Various properties of the front—density, amplitude, flux—are found to increase through much of its lifetime, and when these properties stabilize, it experiences almost no dispersion. This suggests that the wave is traveling through a dispersionless medium.; Through comparison of EUV passbands, I am able to place altitude and temperature constraints on the 13 June 1998 event, and show that the front moves only through the lowest part of the corona, trapped in a wave guide. This analysis is reinforced analytically, by considering a propagating MHD wave in a hydrostatic atmosphere, and through existing theories.; Conclusions offer explanations for the dearth of soft x-ray observations of propagating waves, as well as the seeming uniformity of EUV events. In light of the above-mentioned propagation constraints, I address the usefulness of such waves in coronal seismology. Finally, I discuss how seemingly contradictory theories are merely disparate descriptions of the same kind of event.*; *This dissertation is compound (contains both a paper copy and CD as part of the dissertation). The CD requires the following system applications: QuickTime; Windows MediaPlayer or RealPlayer.