Rapid Auroral Wandering During the Laschamp Event
Abstract
41 thousand years ago, the Laschamp geomagnetic excursion caused Earth's magnetic field to drastically diminish to ∼4% of the modern dipole moment and altered its dipole-dominated structure. 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. In particular, the structure of the magnetosphere during such an event was unconstrained. We present an initial investigation of the global space environment and related plasma environments during several phases of the Laschamp event using an advanced multi-model approach. We use recent paleomagnetic field models of this event to study the paleomagnetosphere going beyond a simple dipole approximation but consider a realistic geomagnetic field configuration. The field is used within the global magnetohydrodynamic model BATS-R-US to simulate 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 direction, have profound effects on the space environment and the ensuing auroral pattern. Magnetopause distances during the deepest phase of the excursion match previous predictions, 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 to low latitudes, 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 Eurasia and Oceania.
- Publication:
-
44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1573M