If the Laschamps geomagnetic excursion happened today, aviation radiation exposure would be radically altered

Earth's magnetic field serves as humanity's primary defense against cosmic radiation, yet this protective barrier remains far from constant. A groundbreaking international study has now investigated how a magnetic field reduction comparable to the historic Laschamps excursion would impact contemporary aviation operations on critical routes such as Helsinki–Dubai and Helsinki–New York.

The planet's magnetic field continuously deflects harmful cosmic radiation and solar particles that bombard Earth from space. However, this protective strength fluctuates significantly over geological time scales. Occasionally, the field undergoes complete reversals, causing magnetic north and south poles to exchange positions entirely.

"The atmospheric and environmental consequences of magnetic field weakening and reversal can prove catastrophic, though these effects remain poorly understood. The potential ramifications demand serious scientific attention," explains Professor Ilya Usoskin from the University of Oulu, principal investigator of the GERACLE project.

This comprehensive research involved scientists from the Sodankylä Geophysical Observatory and the Space Physics and Astronomy Research Unit at the University of Oulu.

The Laschamps excursion represents one of Earth's most significant recent geomagnetic variations, occurring approximately 41,000 years ago. During this event, the magnetic field diminished to roughly 5% of its present intensity while developing a complex multipolar structure. The weakening phase persisted for approximately two millennia, with complete recovery requiring an additional five thousand years.

The research team's findings, published in the Journal of Geophysical Research: Space Physics, utilized sophisticated modeling techniques to reconstruct magnetic field conditions and cosmic radiation patterns throughout the Laschamps excursion. Their analysis incorporated the enhanced OTSO tool developed by Usoskin's research group, the LSMOD.2 paleomagnetic field model created by GFZ Potsdam for historical magnetic field reconstruction, and the team's CRAC:DOMO model for calculating atmospheric radiation penetration and human exposure levels.

The results reveal that cosmic radiation achieved unprecedented atmospheric penetration levels during this period. The compromised magnetic field dramatically reduced the energy threshold required for cosmic particles to enter Earth's atmosphere, dropping from today's 17 gigavolts (GV) to approximately 4 GV.

Simultaneously, regions vulnerable to cosmic radiation bombardment expanded threefold, exposing vast portions of Earth's atmosphere to elevated radiation levels. Critically, this exposure distribution proved highly irregular. The multipolar magnetic field configuration created unpredictable cosmic particle pathways throughout the atmosphere.

"Multipolar magnetic field conditions generate auroral displays in extraordinary locations across the globe," notes Postdoctoral Researcher Pauli Väisänen.

Radiation would increase in unexpected regions

"Our findings demonstrate that aviation radiation risks during weakened magnetic field periods do not increase uniformly across all regions. Instead, geographical exposure patterns shift in completely unprecedented ways that cannot be predicted using current baseline conditions," states Väisänen.

The study specifically modeled radiation exposure scenarios for two contemporary flight routes during the Laschamps event: Helsinki–Dubai and Helsinki–New York. Current understanding indicates that high-latitude northern routes typically experience elevated radiation exposure, while equatorial routes benefit from superior magnetic shielding. However, the Laschamps period findings challenge these established assumptions.

Remarkably, certain high-latitude northern routes—including Helsinki–New York—could have received partial protection through "shielding pockets" created by the multipolar magnetic field configuration. Conversely, the more southern Helsinki–Dubai route would have encountered significantly elevated radiation exposure due to reduced magnetic field protection in that region.

"Recent years have witnessed increasing scientific and regulatory focus on space weather impacts, aviation safety protocols, and cosmic radiation exposure. These research findings contribute crucial new insights to ongoing discussions while providing analytical frameworks for evaluating similar weak-field scenarios affecting modern society," the research team concludes.

"While geomagnetic excursions of this magnitude remain unlikely in the immediate future," Usoskin and Väisänen emphasize, current observational data indicate that Earth's magnetic field has weakened approximately 9% over the past two centuries. Additionally, the South Atlantic Anomaly—a region characterized by particularly diminished magnetic field strength—has continued expanding in recent years.