Sprites are massive but fleeting bursts of light that erupt above thunderstorms, reaching from roughly 40 to 90 kilometers altitude in the thin air between the cloud tops and the edge of space. They were first accidentally captured on video in 1989, and despite lasting only about 55 milliseconds on average, they rank among the largest luminous phenomena on Earth, sometimes spanning tens of kilometers across. Unlike ordinary lightning, which heats a narrow channel of air to extreme temperatures, sprites are cold plasma discharges driven by electric fields that briefly overwhelm the upper atmosphere after a particularly powerful lightning strike below.
How Sprites Were Found
On the night of July 6, 1989, a University of Minnesota research team testing a low-light video camera happened to point it above a distant thunderstorm. The tape captured a brief, vivid flash high above the clouds. It was the first recorded evidence of something pilots and high-altitude observers had been whispering about for decades: strange lights dancing above storms that vanished too quickly to confirm with the naked eye. Space shuttle video recordings acquired between 1989 and 1991 provided 17 additional examples that confirmed these flashes were real and repeatable, not camera artifacts.1Journal of Atmospheric and Solar-Terrestrial Physics. The role of the space shuttle videotapes in the discovery of sprites, jets and elves
The name “sprite” was chosen deliberately for its lighthearted, mythological overtones. Researchers wanted a word that captured the elusive, almost mischievous nature of something that had evaded scientific detection for so long. Since then, the field has grown rapidly, with dedicated observation campaigns across Europe, Asia, and the Americas generating thousands of recorded events.
What Triggers a Sprite
Sprites are produced by a specific chain of events that begins with a powerful cloud-to-ground lightning stroke, almost always a positive one. Positive strokes transfer positive charge from the upper regions of a thundercloud to the ground, and they tend to move larger amounts of charge from higher altitudes than their negative counterparts. When that charge is suddenly removed from the cloud, the electric field above the storm temporarily surges upward into the mesosphere. This field, called a quasi-electrostatic field, can heat electrons to average energies around 5 electron-volts, ionize neutral air molecules, and excite the optical emissions we see as a sprite.2Journal of Geophysical Research: Space Physics. Sprites produced by quasi‐electrostatic heating and ionization in the lower ionosphere
Not every positive lightning stroke produces a sprite, though. The key predictor is something called the charge moment change, which combines how much charge the stroke transfers with the height from which it falls. Research has found that the probability of sprite generation climbs steeply with charge moment change: strokes exceeding about 1,000 coulomb-kilometers within 6 milliseconds produce sprites more than 90 percent of the time, while those below roughly 600 coulomb-kilometers almost never do.3Geophysical Research Letters. Lightning charge moment changes for the initiation of sprites Other analyses have found sharp threshold behavior consistent with this pattern, with the threshold varying somewhat between nights, sometimes sitting around 350 coulomb-kilometers and other times around 600.4Journal of Geophysical Research: Space Physics. Implications of lightning charge moment changes for sprite initiation The variation likely reflects changing conditions in the ionosphere itself, such as its altitude and density, which shift from night to night.
Negative lightning strokes can produce sprites too, but they need to work harder. Modeling suggests that for identical ionospheric conditions, a negative stroke requires a charge moment change roughly 50 percent larger than a positive one to initiate a sprite.5Geophysical Research Letters. Minimum charge moment change in positive and negative cloud to ground lightning discharges producing sprites Because negative strokes rarely achieve such large charge transfers, positive-stroke sprites dominate the observations by a wide margin.
The Different Shapes Sprites Take
Sprites are not all identical flashes. High-speed cameras have revealed at least three major morphological types, each linked to different parent-lightning characteristics. Column sprites are relatively simple, thin vertical structures with streamers that propagate primarily downward. Carrot sprites are broader and more complex, with both upward and downward streamers branching away from a bright central body, giving them a shape reminiscent of their namesake vegetable. Jellyfish sprites are the most spectacular, with wide, diffuse tops and long tendrils hanging below.
The parent lightning’s charge moment change largely determines which type appears. Strokes with large charge moment changes tend to drive the electric field high enough above the breakdown threshold for long enough that both upward and downward streamers develop, producing carrot and jellyfish forms. Weaker strokes can only sustain downward-propagating streamers, yielding column sprites.6Journal of Geophysical Research: Space Physics. Dependence of positive and negative sprite morphology on lightning characteristics and upper atmospheric ambient conditions Electromagnetic measurements confirm this progression: the electrical current carried by a sprite increases with its morphological complexity, from columns to carrots to jellyfish.7Journal of Geophysical Research: Space Physics. Relationship Between Sprite Current and Morphology
Space-based imaging has recently confirmed that these same morphological classes are visible from orbit. The Atmosphere-Space Interactions Monitor instrument aboard the International Space Station has captured column, carrot, and branching sprite structures at ultraviolet wavelengths, matching what ground cameras see from below.8Journal of Geophysical Research: Atmospheres. Sprites Observed by ASIM: First Imaging Data Set and Temporal UV Emission Patterns
Why Sprites Are Red
To a dark-adapted human eye or a sensitive camera, sprites glow a vivid red in their upper portions and sometimes fade to blue or purple at their lowest tendrils. The red color comes from molecular nitrogen, which makes up about 78 percent of the atmosphere. When the electric field excites nitrogen molecules at sprite altitudes, the dominant light emission falls in the so-called first positive band system, a set of spectral lines clustered in the red and near-infrared part of the spectrum.9Geophysical Research Letters. Optical spectral characteristics of sprites
At lower altitudes, where the air is denser and collisions between molecules are more frequent, the blue second positive band of nitrogen and the first negative band of nitrogen ions contribute more to the spectrum.10Journal of Geophysical Research: Atmospheres. Optical Spectra of Small‐Scale Sprite Features Observed at 10,000 fps The result is a distinctive color gradient: vivid red up top, shifting toward blue-purple at the base. This gradient is essentially a map of how air density changes with altitude, because the same nitrogen molecule produces different spectral features depending on how often it collides with its neighbors before re-emitting light.
How Long a Sprite Lasts
Sprites are extraordinarily brief. High-speed cameras operating at thousands of frames per second have long shown that individual streamers develop and fade in just a few milliseconds, but the total event, including the initial brightening and the lingering afterglow, is longer. Recent measurements using neuromorphic sensors, a type of camera inspired by biological retinas that timestamps each pixel’s brightness change individually, found that average sprite durations were about 55 milliseconds.11Geophysical Research Letters. Sprite Durations Measured With a Neuromorphic Sensor That is roughly one-twentieth of a second, shorter than a human blink. It is fast enough that a casual observer staring in the right direction might register only a faint red shimmer they could easily dismiss as imagination.
The internal dynamics of a sprite unfold even faster. Individual streamer heads propagate at speeds on the order of tens of millions of meters per second, crossing tens of kilometers of altitude in a fraction of a millisecond. Capturing these details requires cameras running at 10,000 frames per second or faster, and even at those speeds the brightest features sometimes saturate the sensor before useful spatial detail can be extracted.
Sprite Halos and How Events Begin
Before the distinctive streamer structures of a sprite develop, something else often appears first: a brief, diffuse glow called a sprite halo. Halos are pancake-shaped flashes that show up at the top of the sprite’s altitude range, around 70 to 85 kilometers, and they typically precede the streamer development below them by a few milliseconds.12Geophysical Research Letters. Statistical Characteristics of Sprite Halo Events Using Coincident Photometric and Imaging Data They are thought to represent the initial, large-scale response of the mesosphere to the quasi-electrostatic field surge, before the field becomes concentrated enough at specific points to launch streamers.
Modeling work has shown that small pre-existing density irregularities in the ionosphere can serve as the seeds from which streamers sprout. When the electric field intensifies around a denser patch of ionization, a luminous cap forms around its lower tip, and a streamer eventually emerges from the base of that cap.13Geophysical Research Letters. Formation of sprite streamers at subbreakdown conditions from ionospheric inhomogeneities resembling observed sprite halo structures This helps explain why sprites do not always appear in the same spot above a storm, and why their fine structure varies from event to event: the mesosphere is never perfectly smooth, and the bumps and ripples of electron density that happen to exist at the moment of the parent stroke shape the sprite that follows.
What Kinds of Storms Produce Sprites
You do not get sprites from every thunderstorm. The storms most reliably associated with sprite production are mesoscale convective systems, large organized storm complexes that can cover enormous areas. Analysis of European sprite-producing storms found them to be trailing-stratiform mesoscale systems reaching maximum cloud areas around 120,000 square kilometers. The sprites tended to appear once the stratiform rain region was well developed, during periods when rainfall was increasing in areas with moderate radar reflectivity.14Atmospheric Research. Analysis of thunderstorm and lightning activity associated with sprites observed during the EuroSprite campaigns: Two case studies
This makes intuitive sense. The stratiform region of a large storm complex is where horizontally extensive charge layers accumulate, and positive cloud-to-ground lightning from these regions tends to tap into large reservoirs of charge at relatively high altitudes. A small, isolated afternoon thunderstorm may produce plenty of negative cloud-to-ground lightning, but it rarely builds the kind of charge structure needed for the big positive strokes that launch sprites. The classic sprite-watching scenario is a warm-season night with a large storm system on the horizon, observed from a clear vantage point a few hundred kilometers away, after the storm’s stratiform region has matured.
Sprites and Atmospheric Chemistry
Because sprites ionize and dissociate air molecules across a wide altitude range, they leave chemical fingerprints in the mesosphere. Modeling studies predict that sprite streamers can boost nitrogen oxide concentrations by several orders of magnitude above background levels in the affected volume.15Journal of Geophysical Research: Space Physics. Chemical and thermal impacts of sprite streamers in the Earth’s mesosphere Since nitrogen oxides participate in catalytic cycles that destroy ozone, even localized bursts of these chemicals are of interest to atmospheric scientists.
More detailed chemistry modeling has traced how the initial burst of atomic nitrogen and oxygen produced by a sprite triggers a cascade of reactions affecting ozone, hydroxyl radicals, and other minor species. Notably, elevated levels of nitric oxide and nitrogen dioxide can persist for about an hour after a sprite event, particularly around 60 kilometers altitude. Ozone, hydroxyl, and hydrogen peroxide also show lingering increases in the 40 to 70 kilometer range.16Atmospheric Chemistry and Physics. Chemistry of sprite discharges through ion-neutral reactions Whether the cumulative effect of thousands of sprites worldwide is enough to meaningfully alter global mesospheric chemistry is still debated, but the local perturbations at night are substantial enough to warrant attention.
The Broader Family of Upper-Atmospheric Flashes
Sprites belong to a family of phenomena collectively called transient luminous events, or TLEs. The other major members are elves, blue jets, and gigantic jets, each produced by different physical mechanisms and occupying different altitude ranges.
Elves are rapidly expanding rings of light that bloom outward from a point directly above a lightning stroke, reaching diameters of several hundred kilometers within less than a millisecond. They are caused not by a quasi-electrostatic field, like sprites, but by the electromagnetic pulse that radiates outward from the stroke at the speed of light. When that pulse reaches the lower ionosphere around 80 to 90 kilometers altitude, it can excite emissions and even ionize the air. Analysis of one such event showed that the elve produced significant nitrogen-ion emission at 391.4 nanometers, clear evidence of ionization, and generated an estimated electron density of about 210 electrons per cubic centimeter over a circular region roughly 165 kilometers across.17Journal of Geophysical Research: Space Physics. D region ionization by lightning‐induced electromagnetic pulses
Blue jets and gigantic jets, by contrast, propagate upward from cloud tops rather than appearing in the mesosphere. Blue jets extend to roughly 40 kilometers altitude, while gigantic jets bridge the entire gap from cloud top to ionosphere. Theoretical work has described how conventional lightning leaders can escape from the tops of thunderclouds under the right electrodynamic conditions and propagate upward.18Journal of Geophysical Research: Space Physics. Recent advances in theory of transient luminous events All of these phenomena were essentially unknown before the 1990s. Together they reveal that the region between the cloud tops and outer space is far more electrically active than anyone suspected for most of the history of atmospheric science.
Sounds from the Mesosphere
Despite occurring at altitudes where the air is far too thin to carry audible sound to the ground, sprites do produce detectable acoustic waves in the infrasound range, below the threshold of human hearing. During a dedicated observation campaign, researchers matched infrasound signals to optically confirmed sprites and found that the propagation delays, frequency patterns, and duration of the sound bursts were consistent with sources at 60 to 80 kilometers altitude, with horizontal dimensions matching the optical width of the sprites.19Geophysical Research Letters. Identification of infrasound produced by sprites during the Sprite2003 campaign The sound is generated by the rapid heating of air in the sprite channel and then propagates downward through the stratosphere and troposphere, arriving at ground-based sensors many minutes after the optical flash. You will never hear a sprite, but sensitive microbarograph arrays can pick up the pressure wave it leaves behind.
Sprites Disturb Radio Signals
The ionization a sprite deposits in the lower ionosphere is enough to temporarily alter the way very low frequency (VLF) radio waves propagate through the Earth-ionosphere waveguide. VLF transmitters used for submarine communication and navigation broadcast signals that bounce between the ground and the ionosphere, and any localized change in the ionosphere’s electron density shifts the phase or amplitude of the received signal. Researchers have used these so-called “VLF sprites” as a remote-sensing tool, detecting sprite-induced ionospheric perturbations thousands of kilometers from the storm, and using the perturbation characteristics to estimate the electrical properties of the sprites themselves.20Reviews of Geophysics. Red sprites, upward lightning, and VLF perturbations This technique has the advantage of working regardless of cloud cover or daylight, making it a useful complement to optical cameras.
Sprites on Other Planets
If lightning exists on other planets, sprites and related transient luminous events might too. Jupiter is the most promising candidate. The Juno spacecraft’s ultraviolet spectrograph detected eleven transient bright flashes in Jupiter’s upper atmosphere, with characteristics that researchers have interpreted as possible sprites, elves, or sprite halos.21Journal of Geophysical Research: Planets. Possible Transient Luminous Events Observed in Jupiter’s Upper Atmosphere Numerical modeling has since shown that sprite streamer formation is physically plausible under realistic Jovian atmospheric conditions, though Jupiter’s vastly stronger magnetic field adds complications that do not exist on Earth.22Journal of Geophysical Research: Space Physics. Preliminary Modeling of Magnetized Sprite Streamers on Jupiter Following Juno’s Observations of Possible Transient Luminous Events
On Earth, the magnetic field is too weak to significantly influence sprite streamer propagation, so most models ignore it. On Jupiter, the field is strong enough to confine the motion of electrons along magnetic field lines, potentially reshaping how streamers develop and what they look like. The Jovian detections remain preliminary, and distinguishing upper-atmospheric transient luminous events from meteoroid impacts requires careful analysis of altitude, spectral content, and duration.23Astronomy & Astrophysics. Cloud reflection modelling for impact flashes on Jupiter Saturn, Venus, and even Mars have been discussed as possible hosts for some form of TLE activity, but observational evidence so far exists only for Jupiter.
Watching Sprites Yourself
You do not need a research grant to see a sprite. Amateur observers and storm chasers have been capturing them on consumer-grade cameras for years, and the basic requirements are straightforward: a clear line of sight to a distant, vigorous thunderstorm at night, with the storm itself below the horizon or at least far enough away that you are looking at the cloud tops from the side. A separation distance of 200 to 500 kilometers is typical. You want to be watching the dark sky above the storm, not the flashes within it.
Camera sensitivity matters more than magnification. A DSLR or mirrorless camera set to a high ISO, wide aperture, and video mode can record sprites that the eye might miss. Some dedicated amateur networks use low-light security cameras with wide-angle lenses pointed toward the horizon, recording continuously and scanning the footage later. The best conditions occur during warm-season nights when large mesoscale convective systems are active in the Great Plains of the United States, the Pampas of South America, equatorial Africa, or the maritime continent of Southeast Asia, all regions with frequent large storm complexes. Late evening through the predawn hours, when the stratiform regions of these systems are at their most expansive, is the prime window. Patience helps: even a prolific sprite-producing storm may go ten or twenty minutes between events, and each flash is gone before you can consciously point at it.