See: Martin D. Altschuler, “Atmospheric Electricity and Plasma Interpretations of UFOs,” in Daniel S.  Gilmore, ed., Scientific Study of Unidentified Flying Objects (New York; Bantam Books, 1969), 1164-1172. Available from: Additional information regarding ball lightning and its various properties from: In 2012, Chinese scientists were observing lightning with a simple video camera paired with a spectrometer and inadvertently recorded the first natural occurrence of ball lightning: "First instance of ball lightning captured on video and spectrographs" at Phys.Org (17 Jan. 2014):