We report the detection of a significant ionospheric disturbance in the D-region of Earth's ionosphere which was associated with the massive gamma-ray burst GRB 221009A that occurred on October 9 2022. We identified the disturbance over northern Europe - a result of the increased ionisation by X- and gamma-ray emission from the GRB - using very low frequency (VLF) radio waves as a probe of the D-region. These observations demonstrate that an extra-galactic GRB can have a significant impact on the terrestrial ionosphere and illustrates that the Earth's ionosphere can be used as a giant X- and gamma-ray detector. Indeed, these observations may provide insights into the impacts of GRBs on the ionospheres of planets in our solar system and beyond.
@article{arxiv.2210.15284,
title = {A Significant Sudden Ionospheric Disturbance associated with Gamma-Ray Burst GRB 221009A},
author = {Laura A. Hayes and Peter T. Gallagher},
journal= {arXiv preprint arXiv:2210.15284},
year = {2022}
}