One year in the Earth's magnetosphere: A global MHD simulation and spacecraft measurements

TL;DR

This study presents the longest global MHD simulation of Earth's magnetosphere over a year using real solar wind data, validating the model against spacecraft measurements and magnetic field models.

Contribution

It provides the first extensive year-long simulation of Earth's magnetosphere with real-time solar wind input, validating the model's accuracy and comparing magnetic footprints with established models.

Findings

High correlation between OMNIWeb data and Cluster measurements before the bow shock.

Good agreement between GUMICS-4 simulation footprints and T96 model, especially in the northern hemisphere.

Simulation enhances understanding of magnetospheric responses to solar wind variations.

Abstract

The response of the Earth's magnetosphere to changing solar wind conditions are studied with a 3D Magnetohydrodynamic (MHD) model. One full year (155 Cluster orbits) of the Earth's magnetosphere is simulated using Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS-4) magnetohydrodynamic code. Real solar wind measurements are given to the code as input to create the longest lasting global magnetohydrodynamics simulation to date. The applicability of the results of the simulation depends critically on the input parameters used in the model. Therefore, the validity and the variance of the OMNIWeb data is first investigated thoroughly using Cluster measurement close to the bow shock. The OMNIWeb and the Cluster data were found to correlate very well before the bow shock. The solar wind magnetic field and plasma parameters are not changed significantly from the $L_1$ Lagrange point to the foreshock, therefore the OMNIWeb data is appropriate input to the GUMICS-4. The Cluster SC3 footprints are determined by magnetic field mapping from the simulation results and the Tsyganenko (T96) model in order to compare two methods. The determined footprints are in rather good agreement with the T96. However, it was found that the footprints agree better in the northern hemisphere than the southern one during quiet conditions. If the By is not zero, the agreement of the GUMICS-4 and T96 footprint is worse in longitude in the southern hemisphere. Overall, the study implies that a 3D MHD model can increase our insight of the response of the magnetosphere to solar wind conditions.