St. Elmos Fire during in Flight Refueling of a KC-135

A KC135 is preparing for aerial refuelling of a USAF E-4. The same aircraft used as Air Force One. The meteo conditions that we were going through causes the differential static equalization between the two aircraft. Once the boom touches the receptacle of the E-4 the charges are equalized and the static immediately stops. This situation is commonly known as St Elmos Fire.