The Red Sprites and Blue Jets Above Thunderstorms
Rare Atmospheric Phenomena Explained
Red sprites and blue jets are rare forms of upper-atmospheric lightning that occur high above thunderstorms, producing striking visual phenomena not usually seen from the ground. These flashes take shape in the ionosphere, with red sprites appearing as brief, red-colored bursts above active thunderstorm clouds, while blue jets shoot upward from the tops of thunderstorms as blue or violet streaks. Many people are surprised to learn that these phenomena exist, as they were only documented starting in the late 20th century.
Researchers and photographers have captured these events using sensitive cameras and satellite imagery, revealing their unique shapes and behaviors. The mysterious nature of red sprites and blue jets has led to growing interest among scientists, storm chasers, and space agencies, who continue to study their causes and effects in the atmosphere. These phenomena offer a fascinating glimpse into the complexity of lightning and the dynamic processes occurring far above familiar storm clouds.
Understanding Transient Luminous Events
Transient luminous events (TLEs) are brief, luminous phenomena that occur above thunderstorms, often at altitudes much higher than traditional lightning. These optical events reveal interactions between concentrated thunderstorm energy and the upper atmosphere, offering insights into atmospheric electricity and chemistry.
Defining Transient Luminous Events
TLEs describe a set of electrical discharge phenomena distinct from ordinary lightning. They typically occur tens of kilometers above thunderstorm clouds, in the mesosphere or lower ionosphere.
Most TLEs last for only a few milliseconds, yet can cover large horizontal and vertical distances. These events are generally invisible from the ground due to cloud layers and atmospheric scattering, but they can be captured with sensitive cameras and from aircraft or space.
Their discovery expanded understanding of the atmosphere, linking ground-based weather with processes occurring far above the storm proper. TLEs are studied by meteorologists and atmospheric scientists for their implications in weather modeling and electrodynamics.
Overview of TLE Types
The most widely studied TLEs include red sprites and blue jets, but several other forms exist.
Key TLE Types:
Type Appearance Altitude Range Red Sprites Reddish flashes 50–90 km (mesosphere) Blue Jets Blue cones/beams 16–50 km (stratopause) ELVES Expanding rings ~90 km (lower ionosphere) Gigantic Jets Large blue flashes Up to 90 km
Red sprites typically appear as clusters of reddish vertical streaks.
Blue jets shoot upward from thundercloud tops in narrow cones or wide fans.
ELVES are rapidly expanding, faintly glowing disks caused by electromagnetic pulses.
Gigantic jets are rare and can traverse a larger vertical range than blue jets.
Role of the Upper Atmosphere
The upper atmosphere provides the unique conditions that allow TLEs to form. Thin air at these altitudes reduces electrical resistance, making it possible for high-energy discharges to propagate for tens of kilometers above thunderstorms.
Ionospheric and mesospheric composition affects how electrical energy from traditional lightning spreads upward. The presence of certain gases, pressure differences, and varying levels of ionization all contribute to different TLE behaviors.
These events not only influence local atmospheric chemistry but may also play a part in the global electrical circuit. Studying TLEs helps scientists refine models of energy transfer between thunderstorms and the uppermost layers of the atmosphere.
What Are Red Sprites?
Red sprites are rare atmospheric electrical discharges that occur above thunderstorms. They are usually triggered by strong lightning events and can appear as fleeting red flashes high in the sky.
Formation and Characteristics
Red sprites form in the mesosphere, typically at altitudes ranging from 50 to 90 kilometers (31 to 56 miles) above Earth’s surface.
They appear as clusters or columns of red light, often with tendril-like shapes or branching structures.
A typical red sprite lasts only a few milliseconds, making them difficult to observe without specialized equipment.
Sprites have a reddish hue due to excitation of nitrogen molecules in the upper atmosphere.
Their luminosity is lower than traditional lightning, and they do not produce thunder.
Observers sometimes report blue or purple edges at the lower part of the sprite, resulting from different atmospheric gases being excited.
Connection to Thunderstorms
Red sprites are always associated with large thunderstorms, most often those that produce intense lightning.
They are usually observed above the cloud tops, making them invisible from the ground during storms or under cloudy skies.
Most sightings occur during strong storm systems with frequent lightning, particularly in summer months.
Unlike regular lightning, which travels from cloud to ground or within clouds, red sprites extend upward into the upper atmosphere.
They often occur in groups, following bursts of lightning that are strong enough to disturb the electric field above the storm.
Observations are most common from aircraft, mountaintops, or with sensitive cameras pointing above distant storms.
The Role of Positive Lightning
Red sprites are specifically triggered by powerful positive lightning strokes.
Positive lightning transfers a positive charge from the cloud to the ground, which alters the electric field above the storm.
This sudden change in the electrical environment allows a red sprite to form.
Positive lightning is much less common than negative lightning, but it carries significantly more energy.
When one of these bolts strikes, it can produce electric fields that reach up into the mesosphere, leading to the appearance of a sprite.
Key Points:
Positive lightning is the primary trigger
Sprites follow, rather than precede, a lightning event
Sprites are sensitive indicators of energetic storm activity above thunderstorms
Exploring Blue Jets
Blue jets are a striking atmospheric phenomenon tied closely to thunderstorms. They form distinctively compared to red sprites, have unique characteristics, and are typically observed from high altitudes or space-based platforms.
Mechanism Behind Blue Jets
Blue jets originate from the upper regions of thunderclouds during intense storm activity. They are a type of transient luminous event that rapidly propagates upwards, reaching altitudes of up to 50 km. Unlike typical lightning, blue jets shoot from the top of the thundercloud rather than between clouds or toward the ground.
These discharges are blue due to molecular nitrogen emissions triggered by the high-energy electric fields above storm clouds. The process usually begins after a powerful lightning discharge alters the electric charge distribution in the cloud. This sets conditions for a blue jet to launch skyward. Researchers have noted that blue jets can last up to several hundred milliseconds and display a narrow, conical shape as they ascend.
Differences from Red Sprites
Blue jets and red sprites differ in their formation mechanisms, color, and typical altitudes. While blue jets emerge from the upper reaches of thunderclouds, red sprites appear much higher, at altitudes between 60 and 80 km. Blue jets often feature a strong, bluish hue, whereas red sprites emit a reddish glow due to different atmospheric interactions.
The timing and triggers also differ. Sprites often follow large positive cloud-to-ground lightning strikes, while blue jets are linked to intracloud electrical activity and propagate directly upward. Their shapes are distinctive: blue jets are generally narrower and more column-like, while red sprites often resemble diffuse columns, carrots, or tendrils.
Occurrence and Visibility
Blue jets occur less frequently than regular lightning, and their upward movement makes them hard to spot from the ground. Most sightings come from pilots, astronauts, and specially equipped research aircraft. Recent advancements in imaging from the International Space Station have provided clearer footage of these events.
Due to interference from the atmosphere and cloud cover, blue jets require specific storm conditions for detection. Nighttime observations and high-altitude vantage points dramatically increase the odds of spotting them. The brightness and short duration mean blue jets are best observed using sensitive low-light cameras rather than the naked eye.
Other Related Atmospheric Phenomena
Above thunderstorms, a range of transient luminous events appear alongside red sprites and blue jets. These phenomena each have distinct forms, altitudes, and occur due to specific processes in the upper atmosphere.
Elves: Brief Overview
Elves are rapid, expanding rings of light that form high above thunderstorms, typically at altitudes of about 90 to 100 kilometers. They are caused by powerful electromagnetic pulses from underlying lightning strikes. This energy excites nitrogen molecules, creating a brief reddish-orange glow that lasts just a millisecond.
Unlike sprites or jets, elves are extremely large—often more than 300 kilometers wide—but are difficult to see with the unaided eye. Their occurrence provides insight into the energy transmitted by lightning into the upper atmosphere. They highlight the interaction between thunderstorms and the ionosphere.
Gigantic Jets and Secondary Jets
Gigantic jets extend from thunderstorm tops upward to the lower edge of space, sometimes reaching altitudes near 90 kilometers. They connect the cloud with the ionosphere through direct electrical discharge. Unlike blue jets, which are shorter, gigantic jets span a much larger vertical distance.
Secondary jets are less common and are believed to occur following a primary jet event. They often show similar but muted optical signatures compared to the initial jet. Both types contribute to the vertical transport of electrical energy and help balance the atmospheric electrical circuit.
Key Differences Table
Phenomenon Max Height Duration Visible Color Gigantic Jet ~90 km Up to 1 sec Blue-White Secondary Jet ~40 km <1 sec Blue
Understanding Blue Starters
Blue starters are upward electrical discharges that originate at the tops of thunderclouds and rise to altitudes of 20 to 30 kilometers. They are shorter and less energetic than blue jets, appearing as brief, blue-colored flashes. Blue starters are usually detected by specialized cameras because they are fleeting and faint.
Researchers believe blue starters may be an initial stage in blue jet formation. Their mechanics are linked to intense thunderstorm activity but do not bridge the gap between the storm and the ionosphere. Unlike jets, they rarely extend beyond the middle stratosphere.
Halos and Ghosts
Halos frequently accompany sprites. Appearing as faint, disk-shaped glows at about 75 to 85 kilometers altitude, halos surround the area above a strong lightning stroke. They last only a few milliseconds and serve as an optical signature of the electric field disturbance that can trigger sprites.
Ghosts are a recently identified phenomenon—faint, greenish glows that sometimes follow red sprites. They remain less well understood and are under active scientific investigation. Both halos and ghosts offer information about the complexities of electrical processes within the upper atmosphere. Their detection relies on highly sensitive cameras and optical instruments.
The Science of Atmospheric Electrical Discharges
Atmospheric electrical discharges result from distinct interactions between charged regions within clouds, the ground, and layers of the upper atmosphere. These interactions help explain why rare events like red sprites and blue jets form during thunderstorms.
Electrical Field and Electricity
Thunderstorms generate strong electric fields as updrafts lift ice particles and water droplets, which then separate electric charges inside the cloud. Positive charges often accumulate at the cloud top, while negative charges gather near the base. This arrangement creates an intense field that sets the stage for discharges.
Electricity generated by these fields can reach tens to hundreds of millions of volts. As charge builds, the potential difference increases, sometimes leading to dramatic discharges such as lightning or the more rarely observed blue jets and red sprites. The ionization of air by these discharges briefly allows current to flow, equalizing the charge difference.
Cloud-to-Ground Lightning Interactions
Cloud-to-ground lightning is the most familiar type of discharge. It occurs when the negative charge at the bottom of a thunderstorm cloud is attracted to the positive charge on the Earth’s surface. This attraction creates a conductive channel, releasing a powerful bolt of electricity.
The rapid movement of electrons in a lightning strike can momentarily affect the broader atmosphere. Indirectly, these events can generate vertical discharges that propagate upward toward the upper atmosphere. Occasionally, these upward discharges are observed as blue jets or red sprites, which are distinct from regular lightning but linked by these charge-separated regions.
The Ionosphere and the Stratosphere
The ionosphere is a charged layer above the stratosphere, ranging from about 60 km to 1,000 km above the Earth. Ionization caused by solar radiation allows the ionosphere to conduct electricity and play a role in transmitting atmospheric electrical discharges. When electrical activity in thunderclouds is intense, energy can propagate upward through the stratosphere and into the lower ionosphere.
Red sprites frequently occur near the boundary between the stratosphere and the ionosphere, while blue jets are observed starting just above thundercloud tops and reaching up into the stratosphere. The interaction between electrical discharges and these atmospheric layers explains the occurrence and behavior of these phenomena. The layers' different densities and electrical conductivities shape the appearance and duration of each event.
Role of Lightning in TLE Formation
Red sprites and blue jets are both types of transient luminous events (TLEs) triggered by lightning in thunderstorms. These high-altitude optical phenomena are linked to electrical and energetic processes in the atmosphere, including gamma ray production.
Lightning Types and TLE Activation
Different types of lightning play a crucial role in initiating TLEs. Positive cloud-to-ground lightning discharges, often more powerful and less frequent than negative strikes, are the main triggers for red sprites. These upward events occur above powerful thunderstorms, usually at altitudes from 50 to 90 km.
Blue jets, in contrast, are associated with strong electric activity inside clouds but do not directly result from a single lightning stroke. Instead, blue jets initiate from the top of thunderclouds and travel upward to the stratosphere, reaching heights of up to 40-50 km. This process can be summarized:
TLE Trigger Altitude (km) Red Sprite Positive CG Lightning 50–90 Blue Jet Intra-cloud/Elevated Activity 20–50
Both TLEs demonstrate the diversity of how different lightning types influence optical atmospheric events.
Gamma Rays and Associated Emissions
Lightning not only produces visible light but also generates high-energy emissions, including gamma rays. Terrestrial gamma ray flashes (TGFs) are brief bursts of gamma radiation that originate during thunderstorms, often in conjunction with strong lightning activity.
These gamma ray flashes can be detected from space and are associated with TLEs, highlighting the significant amounts of energy involved in some lightning events. Gamma rays are typically produced during powerful upward lightning discharges, which can contribute to the formation of red sprites and sometimes blue jets, connecting optical and energetic phenomena in the upper atmosphere.
The study of these emissions helps scientists better understand the full range of atmospheric electrical activity linked to thunderstorms.
Observation and Research
Scientific study of red sprites and blue jets relies on direct observation, technological advancements, and systematic data collection. Researchers use both ground-based instruments and space-based systems to identify and analyze these transient atmospheric phenomena.
Ground and Space-Based Detection
Red sprites and blue jets are most often detected during intense thunderstorms, particularly at night when their faint light is easier to capture. Ground-based cameras, including high-speed video and low-light sensors, are placed at strategic observation sites to record these phenomena in real time.
Researchers deploy coordinated networks across storm-prone regions to increase detection rates. Visual observations supplement instrument readings, while field campaigns provide detailed visual evidence that supports data analysis. Recent advances have enabled high-resolution imagery of both events from the ground.
Space-based detection involves instruments on satellites and platforms such as weather balloons. These remote sensing technologies allow observation of wide geographic areas and offer unique vantage points above storms, crucial for identifying events invisible from the ground due to cloud cover or distance.
NASA’s Contributions
NASA has played a significant role in the discovery and understanding of red sprites and blue jets. The agency’s Mesoscale Lightning Experiment and Sprites campaign helped popularize both terms and generate the earliest extensive visual records of these events.
Astronauts aboard the Space Shuttle first captured images of sprites and jets in the 1990s, leading to greater scientific interest. NASA continues to use both manned and unmanned missions to observe these phenomena, providing important datasets and fostering international collaboration among atmospheric researchers.
NASA archives and shares data through publicly available platforms. This open approach has allowed researchers globally to access and analyze a wide range of high-quality sprite and jet observations, helping to refine models of their formation and occurrence.
Use of Satellites in Monitoring
Satellites equipped with optical and lightning detection instruments are essential for monitoring sprites and jets. They provide persistent, large-scale coverage that is vital for studying events over oceans and remote land areas where ground-based setups are not practical.
Key satellite instruments, such as photometers and sensitive video cameras, enable the identification of both red sprites and blue jets occurring above thunderstorms. Satellite data helps scientists map occurrences, measure altitudes, and analyze physical characteristics of these transient events.
Satellite monitoring has led to the development of global databases. These resources support efforts to understand atmospheric electricity and links between upper-atmosphere phenomena and standard lightning, advancing knowledge of Earth’s weather and climate systems.
