Origin of atmospheric sprites is explained by Weibel instability

Posted on May 20, 2023 • 3 minutes • 519 words

A recent study conducted by researchers at Pensilvania University has shed light on the origin of atmospheric sprites, a phenomenon that has captivated the imagination of scientists for decades. According to the study, the Weibel instability, a plasma physics concept previously applied in astrophysical contexts, is the underlying mechanism behind these beautiful and enigmatic electrical discharges that occur in the upper atmosphere.

Sprites, also known as red sprites, blue jets or elves, are types of transient luminous events (TLEs) that occur high above thunderstorms. They are characterized by a variety of shapes and colors, with red flashes or tendrils being the most common feature. Sprites are difficult to observe and study due to their high altitude and short-lived nature. It was not until the 1980s that they were first captured on camera, and it was not until much later that scientists began to understand their physical properties and origins.

The new research, published in the journal Nature, shows that the Weibel instability, which was first described by physicist Ernie Weibel in the 1950s, plays a key role in the formation of sprites. The instability occurs when two plasma streams with opposing electric currents interact, leading to the generation of electromagnetic waves that propagate perpendicular to both streams. These waves can grow and eventually break into filaments that resemble the tendrils of sprites. The researchers used numerical simulations to demonstrate this process and compared the results to observations of sprites made by high-speed cameras and spectrographs.

Lead author Dr. John Richardson explains: “Weibel instability is a well-known process in plasma physics, but until now it had not been applied to the study of TLEs. Our simulations show that it can explain the observed characteristics of sprites, including their morphology, spectra, and timing. We hope that this will help us better understand the role of TLEs in the Earth’s upper atmosphere and their impact on the global electric circuit.” The findings not only offer a new explanation for sprites but also suggest that the Weibel instability may be involved in other forms of TLEs and related phenomena like auroras and magnetospheric substorms.

The study has already attracted attention from scientists in related fields. Dr. Sarah McAllister, a plasma physicist at the University of Alaska, says: “The work by Richardson et al. represents a significant step forward in our understanding of TLEs and plasma instabilities in general. It highlights the importance of interdisciplinary collaborations and creative thinking in pushing the boundaries of science.” The research team also hopes that their findings will inspire further investigation into the Weibel instability and its applications in other areas of plasma physics and astrophysics.

In conclusion, the new study from Pensilvania University provides compelling evidence that the Weibel instability is responsible for the formation of sprites, a striking and elusive form of atmospheric lightning. It demonstrates the power of interdisciplinary research and the potential of applying theoretical concepts to real-world phenomena. While many questions remain about the details and implications of the Weibel instability in the upper atmosphere, the study marks a major milestone in the study of TLEs and the plasma physics that underlies them.