Timescale of geomagnetic polarity reversals

Ascertain the duration of Earth’s geomagnetic polarity reversal process and characterize the temporal evolution of geomagnetic field strength during reversals (e.g., the Gauss–Matuyama reversal at 2.58 Ma) to assess the modulation of cosmic radiation shielding.

Background

The paper links potential increases in incident radiation during heliospheric changes with Earth’s variable magnetic shielding. During geomagnetic reversals, the dipole field can weaken substantially, potentially increasing atmospheric exposure to charged particles.

The authors explicitly state that the duration of the reversal process is unknown, although it is generally thought to take a few thousand years, highlighting a key uncertainty for quantifying radiation impacts during such periods.

References

When the Earth's magnetic field reverses polarity, as has occurred at irregular intervals many times in the geologic past69, the geomagnetic field can decrease by nearly an order of magnitude70. It is not known how long this process takes, though it is generally thought to be a few thousand years68.

— Increased and Varied Radiation during the Sun's Encounters with Cold Clouds in the last 10 million years  (2601.11785 - Opher et al., 16 Jan 2026) in Conclusions and Discussion