It is prolonged, if it appears. In most places where you can view it (typically sunset over oceans?) it lasts seconds. The flash still relies on the air conditi

It is prolonged, if it appears. In most places where you can view it (typically sunset over oceans?) it lasts seconds. The flash still relies on the air conditions being amenable above where the sunset is. It's not uncommon for the horizons to be hazy because of blowing snow in your line of sight, or for there to be clouds, etc. But the Sun can be at the right elevation below the horizon for minutes to hours. Byrd claimed it lasted over 35 minutes during his expedition in 1929.