A cosmic-ray detector built to study particles from space has become an unexpected tool for measuring thunderstorm electricity. The GRAPES-3 muon telescope, located in India, detected electrical potential differences inside thunderclouds far exceeding any measurements taken directly within storms.
The instrument records how cosmic-ray particles interact with electric fields in thunderclouds. When these high-energy particles pass through the intense electrical environments, they create detectable signatures. Earlier observations revealed the clouds could generate electrical potentials much stronger than scientists previously confirmed through direct measurement.
However, the telescope spotted a puzzle. The detector recorded significantly more thunderstorm events when storms appeared in the eastern portion of its viewing field compared to the western side. This asymmetry suggested something systematic was affecting the measurements across different directions.
A new study published in the Journal of Cosmology and Astroparticle Physics solved this mystery. The research team, the same group operating GRAPES-3, explained the directional bias in their detection pattern.
The GRAPES-3 muon telescope works by tracking secondary particles created when cosmic rays strike Earth's atmosphere. These particles pass through thunderclouds, and intense electric fields within the storms alter the particle paths in measurable ways. By analyzing how the particles scatter, researchers can infer the strength of the electrical fields generating those deflections.
This application represents a creative use of cosmic-ray physics. Rather than simply measuring space particles, the detector reveals details about terrestrial electrical phenomena that remain difficult to study through conventional methods. Thunderstorm electricity remains poorly understood because direct instruments struggle to survive the violent environment or reach the most intense field regions.
The finding that thunderclouds develop such extreme electrical potentials explains some features of lightning formation and suggests the physics of storm electrification may differ from current models. The ability to probe these fields using cosmic rays offers a new window into one of Earth