The Radiation Power Density of a Natural Ball Lightning Estimated by Its Spectra

Abstract The energy and its source of ball lightning (BL) have long been a mystery. At present, there is no consensus on the energy source of BL. The radiation power density and its evolution of a BL are investigated based on its spectra for the first time. The results show that the radiation power density calculated by O I spectral lines is the highest, and its average value is about 37.40 × 10 7 W/m 2 . The average radiation power densities calculated by Si I and Fe I spectral lines are only around 3.04 × 10 7 W/m 2 and 2.56 × 10 7 W/m 2 , which remained basically steady during the stable luminescence stage. The spectral and energy feature indicated that the BL maybe exist a core with higher energy. The radiation power density shows a periodic pulse feature in the energy core and maintains basically stable in the bright periphery with lower energy. The highest energy of this BL can only excite light radiation of the near infrared band from the O I atoms in the air. The BL moved toward the nearby power line. Deduced from the energy distribution and moving direction that this BL should be associated with small gap intermittent discharge at the bottom of previous cloud‐to‐ground (CG) lightning channel, meanwhile, the strong atmospheric electric field during thunderstorm and its distribution should be a potential outside source that drives the discharge and moving direction of this BL. This work has important reference significance to reveal the mystery of BL and the application of BL phenomenon.