Thunderstorms would exaggerate the intensity of gamma rays measured at high-altitude observatories, according to Science

Dec. 23 () –

Several scientists have pointed out that Thunderstorms could be exaggerating the intensity of gamma rays measured in 2021 by the High Altitude Air Shower Observatory (LHAASO) (located in the Chinese area of ​​Tibet), as reported by Science in an article. For its part, LHAASO has reported that sees no “obvious connection” between PeV gamma ray events and thunderstorms and that, in any case, thunderstorms are relatively rare in the mountains of Tibet.

Specifically, LHAASO detected the highest-energy light in the universe: a handful of gamma-ray photons that reach energies of more than one petaelectronvolt (PeV). However, as specified by Science, the observatory does not capture gamma rays directly, but rather showers of subatomic particles generated when an ultra-high energy gamma ray hits the upper atmosphere.

With this in mind, astrophysicist Ashot Chilingarian, director of the Aragats Cosmic Ray Research Station, said last month in a study in The Astrophysical Journal Letters that “Powerful” electric fields from a thunderstorm can intensify these particle showerswhich would cause LHAASO astronomers to overestimate the energy of the original gamma ray. Therefore, he asked that LHAASO publish the meteorological data associated with its gamma ray claims to demonstrate that thunderstorms are not confounding the measurements.

In September, he and colleagues presented evidence that electric fields in thunderstorms could be stronger than previously believed based on an analysis of 56 thunderstorms at a mountaintop observatory in Armenia. In this new study, the expert and researcher Mary Zazyan, from the Yerevan Institute of Physics, modeled the effect of such an electric field on a particle shower at LHAASO and found that the number of high-energy particles increased significantly. significant. This, they argued, would cause researchers to vastly overestimate the energy of the gamma-ray source.

Furthermore, Johannes Knapp, an astroparticle physicist at DESY, a particle physics laboratory in Germany, has stated that the effects of thunderstorms are “plausible” and that astronomers at LHAASO and other high-altitude gamma-ray observatories should be aware of them. into account. “If by chance some of these events occur during a thunderstorm, the rain particles could be amplified by a factor of 10 or 100“, he gave as an example.

For his part, LHAASO spokesperson Zhen Cao stated that his team already monitors the weather and deploys antennas to measure atmospheric electric fields. In turn, he has pointed out that he sees no “obvious connection” between PeV gamma ray events and thunderstorms and that, in any case, thunderstorms are relatively rare in the mountains of Tibet.

Kelly Malone, a scientist at Los Alamos National Laboratory (LANL) and member of the HAWC collaboration, explained that researchers at the Cherenkov High Altitude Water Observatory (HAWC) in Mexico also monitor electric fields and verify their data to detect storms. that may cause confusion. In this sense, he has stressed that ultra-high energy gamma rays are distributed “uniformly” in time throughout his data, “which would not be true if they were attributed to thunderstorms.”

For his part, Pat Harding, a LANL scientist who leads the HAWC collaboration, has acknowledged that a “more mundane” reason for doubting whether thunderstorms are contaminating HAWC’s gamma ray events is that the team, It often does not save data during extreme weather conditions. “The main reason for that, honestly, is that our experiment is often interrupted during thunderstorms,” has admitted.

In addition, he stressed that he does not mind that LHAASO’s record detections are subject to additional scrutiny since “in cases where there are only one or two specific events that generate a lot of excitement” we must “open it up as much as possible for people to try to investigate.”