Transient Luminous Events: The Electrifying Phenomenon Illuminating our Skies (Credit: NASA)

Upper atmospheric lightning, also known as a transient luminous event, is an electrifying phenomenon that is not easily studied in the same way as “normal” tropospheric lightning that occurs in a typical thunderstorm.  The European Space Agency Atmosphere-Space Interactions Monitor (ASIM) aboard the International Space Station is a collection of optical cameras and photometers along with a x and gamma ray detector that is used to detect the electrical discharges from upper atmospheric thunderstorms that make up transient luminous events.  But what exactly are the different types of transient luminous events?

Sprites refer to the flashes that result from electrical breakdown in the mesosphere and can be triggered by the electrical discharges of positive lightning strikes between the thunderstorm and the ground.  The term sprite is actually an acronym for Stratospheric/mesospheric Perturbations Resulting from Intense Thunderstorm Electrification. Sprites typically appear as reddish-orange or greenish-blue flashes with hanging branches at the bottom and arcing branches at the top.  Another type of transient luminous event with an equally whimsical sounding name are elves. Elves is an acronym for Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources and refer to the dim, flattened glow that occurs in the ionosphere from the excitation of nitrogen molecules caused by electron collisions.

Another type of transient luminous event are jets, which can refer to both blue jets and gigantic jets.  Blue jets are upward reaching lightning discharges that can reach into the stratosphere. “Normal” lightning discharges that occur between a positive charge region at the top of a thunderstorm and a negative charge layer above it can lead to a bright blue flash of lightning, or blue jet.  The blue color is likely a result of blue emission lines through neutral and ionized molecular nitrogen. Gigantic jets differ from blue jets in that they initiate between that upper positive charge layer and a lower negative charge layer toward the bottom of the thunderstorm cloud. Gigantic jets can reach high levels of the atmosphere and typically changes color from blue to red as it reaches higher into the atmosphere.

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©2019 Meteorologist Stephanie Edwards ​