Abstract
41 thousand years ago, the Laschamps geomagnetic excursion caused
Earth’s geomagnetic field to drastically diminish to
~4% of modern values and modified the geomagnetic
dipole axis. While the impact of this geomagnetic event on environmental
factors and human lifestyle has been contemplated to be linked with
modifications in the geospace environment, no concerted investigation
has been conducted to study this until recently. We present an initial
investigation of the global space environment and related plasma
environments during the several phases of the Lachamps event using an
advanced multi-model approach. We use recent paleomagnetic field models
of this event to study the paleomagnetosphere with help of the global
magnetohydrodynamic model BATS-R-US. Here we go beyond a simple dipole
approximation but consider a realistic geomagnetic field configuration.
The field is used within BATS-R-US to generate the magnetosphere during
discrete epochs spanning the peak of the event. Since solar conditions
have remained fairly constant over the last ~100k years,
modern estimates of the solar wind were used to drive the model.
Finally, plasma pressure and currents generated by BATS-R-US at their
inner boundary are used to compute auroral fluxes using a stand-alone
version of the MAGNIT model, an adiabatic kinetic model of the aurora.
Our results show that changes in the geomagnetic field, both in strength
and the dipole tilt angle, have profound effects on the space
environment and the ensuing auroral pattern. Magnetopause distances
during the deepest phase of the excursion match previous predictions by
studies like Cooper et al. (2021), while high-resolution mapping of
magnetic fields allow close examination of magnetospheric structure for
non-dipolar configurations. Temporal progression of the event also
exhibits rapid locomotion of the auroral region over
~250 years along with the movement of the geomagnetic
poles. Our estimates suggest that the aurora extended further down, with
the center of the oval located at near-equatorial latitudes during the
peak of the event. While the study does not find evidence of any link
between geomagnetic variability and habitability conditions, geographic
locations of the auroral oval coincide with early human activity in the
Iberian peninsula and South China Sea.