Fluid motions in the solar atmosphere. I - On the origin and decay of spicules. II - A spicule model with emission lines

Using a time-dependent numerical method including the effects of radiation, thermal conduction, mechanical heating and ionization of hydrogen, we have investigated the origin and decay of solar spicules. The results show that a spicule could be regarded as the matter which follows behind the chromosphere-corona transition region, which is pushed upward into the corona by an impulsive wave event. The spicule declines gradually and shows recurrent behavior due to the radiative loss and the oscillation of the atmosphere. Our calculations provide a reasonable explanation of the observed characteristics of spicules, such as height, velocity, lifetime and density etc