Propagating and Stationary Bright Knots in the Quiet Sun

The question of what heats the solar chromosphere and corona remains one of the most important puzzles in solar physics and astrophysics. Up to now, two mechanisms are considered to work in heating the chromosphere and corona: magnetic reconnection and wave (turbulent flow) dissipation. But it is still not understood which mechanism is dominant. To solve the heating problem, one important topic at this stage is that we should understand how much energy is contributing from the two mechanisms respectively to the heating. In the quiet Sun, the thermal energy signal is observed as brightenings. Here we report two kinds of bright knots with a total of 3605 in the chromosphere of the quiet Sun, using the data from the New Vacuum Solar Telescope at Yunnan Observatories. The first kind of 1537 bright knots, which is first detected in chromospheric fibrils where waves and their dissipation are ubiquitous, propagates along these fibrils with velocities from 5 to 69 km s−1. The second kind of 2068 knots keeps stationary, and always appears at the footpoints of these fibrils where network magnetic fields exist, suggesting that magnetic reconnection locally produces these stationary knots. Based on the observations of thousands of bright knots, we display the different distribution patterns of the two kinds of bright knots in the quiet Sun, and deduce that half of the energy for heating the chromosphere is supplied by wave dissipation, and the other half by magnetic reconnection.