An elf appeared above the Iota storm

On November 14, tropical storm Iota passed over Puerto Rico. Soon becoming a category 5 hurricane, the increasing storm provoked the appearance of powerful lightning. Frankie Lucena pointed his video camera at the storm and saw a huge red disk of light flash over the outer edges of the storm. It appeared and disappeared in a split second.

This was a phenomenon called an elf (ELVES, Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources). The abbreviation is translated from English as"light emission and very low-frequency disturbances due to a pulse from an electromagnetic source".

The elf was first spotted in 1990 using cameras on the space Shuttle. It is the result of the fact that the pulse of electromagnetic radiation from lightning propagates upwards, hitting the base of the ionosphere. At the same time, elves appear at an altitude of about 100 km above storms and do not last more than a few milliseconds, which makes them elusive to the human eye. That's also why they were open so late. The reddish glow can extend for hundreds of kilometers.

The lightning that triggered this elf's appearance was indeed very powerful. According to Stephen Kammer of Duke University, the current reached 381 kiloamperes. For comparison, the current strength in conventional lightning is only 10-30 kiloamperes.