Recorded for the first time just a few decades ago, the strange, firework-like displays of bright red light that sometimes occur over thunderstorms continue to mystify scientists. Now, researchers in China are using state-of-the-art technology to better understand what causes the vertical, alien-like streaks known collectively as "sprites".
To start, the team looked for parent lightning strokes of 38 red sprites seen in China on July 30, 2015, during an atmospheric event called a mesoscale convective system (MCS). During an MCS, a collection of thunderstorms act as a system, and this six-hour storm in July just so happened to be one of the best.
“This is probably the most productive sprite-producing thunderstorm system ever reported in China,” said study author Dr LU Gaopeng in a statement.
Sprites appear above thunderstorms so high and rapidly – often in just tens of milliseconds – that they are difficult to study. They occur when offshoots of electricity discharge high above thunderstorm clouds in the mesospheric region around 40 to 90 kilometers (25 to 56 miles) above the Earth. These extremely rare displays of upper-atmospheric electromagnetism fall into the category of transient luminous events.
The collection of sprites were observed using a long-baseline lightning location network of low and very-low-frequency magnetic field sensors, noted the authors in the journal Advances in Atmospheric Sciences.
"Based on the broadband magnetic fields measured at six stations of LERP [Lightening Effects Research Platform], we applied an optimization method of lightning location based on a grid search with CUDA parallel computing architecture to efficiently obtain the location of parent strokes (SP+CGs) for these sprites," they wrote.
The team found that almost half of all sprites occurred once a thunderstorm reaches maturity, which is the most intense point of the storm. Furthermore, these sprites behaved in much the same way as others produced in North America and Europe.
Also known as jellyfish lightning, sprites are red in coloring and have a wide, bell-shaped top with shoots of light jutting from the bottom. We’ve known about their existence for decades, but only recently have scientists determined where they come from. Red sprites only occur during thunderstorms and are predominantly produced by energy positive cloud-to-ground strokes.
Scientists hypothesize they are caused by either a collision of high-energy electrons with air molecules or irregularities in the mesosphere caused by gravity waves. Because they occur in the atmosphere level where radio communication takes place, they have been known to interfere with long-range communication signals.
3
