“A compact intracloud discharge (CID), also known as a narrow bipolar event (NBE) or narrow bipolar pulse (NBP) is an intensive form of lightning that produces radio waves and scarce visible light. Lasting only a few millionths of a second (typically 20 us), these events are the most powerful known natural terrestrial source of radio waves in HF and VHF band.”
To date, the physical processes behind CIDs have not been explained :
“Despite the multi-year studies of CIDs and the signiﬁcant volume of experimental data accumulated to date, the nature of this phenomenon is in many respects unclear.”
Source: Radiophysics and Quantum Electronics, Vol.58, No.7, 2015
Ideas for new topics, and suggested additions / corrections for old ones, are always welcome.
If you have skills or interests in a particular field, and have suggestions for Wikenigma, get in touch !
Or, if you'd like to become a regular contributor . . . request a login password. Registered users can edit the entire content of the site, and also create new pages.
( The 'Notes for contributors' section in the main menu has further information and guidelines etc.)