Recent observations from NASA’s ER-2 aircraft have given us a deeper view into gamma rays produced by thunderstorms. This high-altitude plane, flying over thunderclouds in the Caribbean and Central America, has captured views of invisible bursts of radiation, providing fresh insights into their formation and characteristics. The aircraft’s ten flights revealed that the previously known types of gamma-ray emissions are more complex and frequent than scientists had anticipated.
The Complexities of Gamma Rays
Researchers identified two main forms of gamma rays: terrestrial gamma-ray flashes (TGFs), which are brief but intense bursts, and gamma-ray glows, which are dimmer yet longer-lasting emissions. The ER-2’s data also introduced a new category: flickering gamma-ray flashes, which present a middle ground in brightness and duration.
David Smith, a physicist at the University of California, Santa Cruz, expressed his astonishment at these findings, calling them the most significant in this field for over a decade.
A Bird’s Eye View of Storm Activity
The ER-2 ascended to approximately 20 kms (12.4 miles) during its mission. This allowed it to observe the thunderstorms’ gamma-ray activity from a unique vantage point. As the aircraft is equipped to transmit data in real-time, the aircraft could revisit regions where gamma-ray activity was high. This lead to a more comprehensive understanding.
The researchers discovered that gamma-ray glows could persist for hours and cover vast areas, measuring thousands of square kms. Notably, these glows were found to fluctuate in intensity over seconds, challenging previous assumptions about their stability.
New Discoveries and Implications
The study also revealed numerous TGFs that were too faint for satellite detection, suggesting that prior observations might have underestimated their prevalence. This discovery could reshape our understanding of gamma-ray emissions in thunderstorms.
The flickering gamma-ray flashes, which comprise rapid, repeated pulses, offer valuable clues about the mechanics of thunderstorms. Many of these flashes were closely followed by lightning strikes, indicating a possible link between the two. Researchers hypothesise that these flickering emissions may serve as precursors to lightning, potentially influencing the electric fields within thunderclouds.
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