Solar Spicules: Recent challenges in observations and theory
Spicules are jets of cold chromospheric plasma flowing upwards into the hot corona. They have been intensively studied during decades both, observationally and theoretically. However, there are still many unanswered questions in their formation and dynamics. The paper summarizes recent progress in the study of spicules. Particular attention is paid to the recently developed two-dimensional rebound shock model, which may explain observed double-thread structure and quasi-periodic appearance of spicules. It is also suggested that observed high speed flow in recently discovered type II spicules may undergo Kelvin-Helmholtz instability, which may lead to their rapid disappearance and consequently may explain their shorter lifetime. © 2011 American Institute of Physics.