Longitudinal and transverse waves in solar coronal loops: Overview of recent results (Invited)

Abstract:

Recent observations have revealed the ubiquitous presence of magnetohydrodynamic (MHD) waves and oscillations in the solar corona (mainly in active region loops). The study of MHD waves is motivated by two major goals in solar physics, namely coronal seismology and the role of MHD waves in coronal heating. The SDO/AIA with a large field of view (full Sun) and high spatio-temporal resolutions not only provides us more opportunities to captue the flare-excited oscillation events that were ever seldom observed but also allows us to explore their details for better understanding the wave excitation, propagation and damping mechanisms. Spectroscopic observations by the Hinode/EIS reinforce the capability of imaging instruments in identification of various wave modes. In this talk I will briefly review recent results in observational studies of longitudinal and transverse waves. The talk focuses on four kinds of wave phenomena in coronal loops: (i) Flare-excited standing slow-mode waves in hot loops, (ii) Persistently propagating slow magnetosonic waves and outflows in fan-like loops, (iii) Impulsively-excited standing kink loop oscillations, (iv) Persistently propagating transverse Alfvenic (kink) waves. I will discuss the relevant debates in their interpretations, and the possible impacts of new results on the current wave theories concerning applications of coronal seismology.