During thunderstorm discharges in the Earth’s atmosphere, very low-frequency (whistling) plasma waves are produced. The authors of a new study discovered that the whistling can travel much farther than previously thought, posing a potential danger to satellites operating in orbit and astronauts.

During a lightning discharge, a large amount of energy is released, some of which is converted into special electromagnetic waves (whistling atmosphere or whistles). These waves have circular polarization and propagate along the lines of force of the planet’s magnetic field. They are usually recorded in the frequency range from 100 hertz to 10 kilohertz.

For decades, researchers believed that the whistlers’ range was limited to about a thousand kilometers above the Earth’s surface, where they disappeared and dispersed.

Two American physicists Vikas Sonowalkar (Vikas Sonwalkar) and Amani Reddy (Amani Reddy(from the University of Alaska Fairbanks) challenged the previous view on the distribution of whistlers in the Earth’s atmosphere. Scientists confirmed that some plasma waves interacting with the ionosphere can reflect off it and penetrate deep into the Earth’s magnetosphere, up to 20,000 kilometers high.

According to researchers’ calculations, whistlers can carry twice as much energy as expected. This energy, penetrating the magnetosphere, accelerates charged particles, creating electromagnetic radiation that can disrupt satellites, damage their equipment, and even harm astronauts in orbit. Sonuwalkar and Reddy wrote in their paper published in the journal Science Developments.

Physicists found evidence of whistlers bouncing off the ionosphere in data taken by the two Van Allen Probes, twin spacecraft that studied Earth’s radiation belts from 2012 to 2019. The existence of such whistler atmospheres is also indicated by indirect data published in early studies conducted by other scientists in the 1960s.

The authors of the new scientific paper noted that information collected from the Van Allen Probes satellites and archival scientific publications points to the large-scale nature of this hitherto unnoticed process. In other words, the phenomenon described in the Sonuwalkar and Reddy article occurs quite often in the atmosphere, but for a long time nothing was known about it.

In the near future, physicists plan to collect and process additional information from other satellites about new types of whistling atmospheres that can penetrate the Earth’s magnetosphere 20,000 kilometers away.

The scientists’ discovery raises the issue of space safety, which is especially important in the context of climate change. Global warming could lead to an increase in the frequency and intensity of thunderstorms and, consequently, an increase in the impact of whistlers on the magnetosphere, which would require the development of new methods to protect spacecraft and crew.