Reassessment of Ionospheric Responses to GRB~221009A: Disentangling Instrumental, Illumination and Geophysical Effects

TL;DR

This study critically reevaluates claims that the bright GRB 221009A affected Earth's ionosphere, finding that observed anomalies are due to natural geophysical processes and instrumental effects, not the burst itself.

Contribution

It provides an independent reassessment with expanded datasets, clarifying that reported ionospheric responses are unrelated to the GRB and are caused by other factors.

Findings

No coherent TEC enhancement linked to the GRB.

Electric-field anomalies are related to illumination conditions.

EEJ fluctuations are associated with solar-wind variability.

Abstract

Gamma-ray bursts (GRBs) have long been proposed to perturb Earth's ionosphere, with occasional reports of disruptions in ultra- and extremely-low-frequency radio signals. The exceptionally bright GRB~221009A was recently claimed to induce multi-altitude ionospheric responses, including perturbations in satellite electric fields, regional total electron content (TEC), and the equatorial electrojet (EEJ). These claims have renewed interest in the potential near-Earth impacts of astrophysical transients. Here we perform an independent reassessment using expanded datasets spanning multiple altitudes. We find no coherent, burst-like TEC enhancement, show that the reported electric-field anomalies recur under specific illumination conditions each orbit, and demonstrate that the EEJ fluctuations preceded the burst and coincide with solar-wind variability. Together, these results indicate that the reported GRB-induced ionospheric responses are fully attributable to other natural geophysical processes and instrumental artefacts, thereby resolving a high-profile controversy and clarifying the true limits of GRBs'ionospheric effects.