Fluorescence caused by ionizing radiation from ball lightning: Observation and quantitative analysis

•Eyewitness saw blue ball lightning before a clear glass window that glowed yellow.•The window fluoresces only with radiation at wavelengths shorter than 375 nm.•Estimated total of 10–100 W of radiation <375 nm probably emitted from object.•This observation supports plasma theories of ball lightning.

Ball lightning is a rare phenomenon, typically appearing as a glowing sphere associated with thunderstorms. In 2008 one of the authors witnessed a blue ball-lightning object hover in front of a glass window that appeared to glow yellow. Calibrated quantitative fluorometry measurements of the window show that the glow was probably due to fluorescence caused by ionizing radiation (UV or possibly X rays). Based on the measurements performed, estimates of the total ionizing-radiation power emitted by the object range upward from about 10 W. These are among the most reliable semi-quantitative measurements so far of ionizing-radiation output from a ball-lightning object.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide