Dynamics of Descending Knots in a Solar Prominence and Their Possible Contributions to the Heating of the Local Corona

The knots in solar prominences are often observed to fall with nearly constant velocity, but the associated physical mechanism is currently not well understood. In this Letter, we present a prominence observed by the New Vacuum Solar Telescope in H_α wavelength. Knots that rose within the prominence appear to have been preferentially located at higher altitude, whereas those that fell were found throughout the entire prominence structure. The descending speed of the knots near the solar surface was higher than that far away from the solar surface. We noted that the knots near the solar surface may run along a set of coronal loops observed from the Atmospheric Imaging Assembly. Elsewhere, the majority of knots are interpreted to have descended across more horizontal magnetic fields with a nearly constant speed. This lack of acceleration indicates that the liberated gravitational potential energy may not manifest as an increase in kinetic energy. Assuming instead that the descending knots were capable of exciting Alfvén waves that could then dissipate within the local corona, the gravitational potential energy of the knots may have been converted into thermal energy. Assuming a perfectly elastic system, we therefore estimate that the gravitational energy loss rate of these observed knots amounts to ≈1/2000 of that required to heat the entire quiet Sun, increasing to 1/320 when considering possibly further downward motions of the knots having disappeared in the H_α observations. This result suggests such a mechanism may contribute to the heating of the corona local to these prominences.