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What do you understand by "Saint Elmo's Fire"?
  • A
    A bright blue or violet glow visible around the windscreen and external parts of the aircraft, occasionally seen when flying in the vicinity of thunderstorms.
  • B
    A natural light display in the sky, caused by charged particles in the solar wind reacting with particles in the upper atmosphere.
  • C
    A natural light display in the sky, often seen by pilots flying at high altitude in Northern latitudes only.
  • D
    A bright blue glow visible very briefly after a damaging lightning strike.

Refer to figure.

ST. ELMO'S FIRE

Besides lightning, another atmospheric electrical phenomenon associated with thunderstorms is St. Elmo's fire, which forms when the air is ionised around a conductor and has small electrical discharges around it. This can happen to an aircraft flying through heavily charged skies. St. Elmo's fire can only be seen during the night and it is usually bluish or violet in colour but can also have a greenish tinge. It typically occurs on sharp and pointed objects such as ships or the wingtips of airplanes in strong electric fields inside or close to a thunderstorm, but it can also form on the windshield of airplanes.

While not a hazard in itself, St Elmo's Fire is an indication of thunderstorm activity and may be a precursor to a lightning strike.

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