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

Abstract

The response of the Earth's magnetosphere to changing solar wind conditions is studied with a 3-D 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 are 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 are 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 B y 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 3-D MHD model can increase our insight of the response of the magnetosphere to solar wind conditions.

Unusual Location of the Geotail Magnetopause Near Lunar Orbit: A Case Study

“…Recently, many studies have employed global MHD models to study the effect of the IMF in the cross‐section of the magnetotail at lunar distance. Their results confirmed that the twisting of magnetopause results from nonzero IMF B Y (e.g., Facskó et al, ; Gordeev et al, ; Sibeck & Lin, ; Vörös et al, ; Wang et al, ). They also demonstrated that the magnetopause could elongate further along the direction of IMF in the distant magnetotail than in the near‐Earth regions.…”

Testing Efficiency of Empirical, Adaptive, and Global MHD Magnetospheric Models to Represent the Geomagnetic Field in a Variety of Conditions

“…One of the reasons for that is a rare use of global simulations for mapping to the ionosphere, the other-existing problems in the near-Earth region. This type of comparison was reported in a work by Facskó et al (2016), where the authors compared the ionospheric foot points from Grand Unified Magnetosphere Ionosphere Coupling Simulation version 4 and from the T96 empirical model. The determined footprints were in overall agreement (foot point difference in a range 200-600 km) with the T96 in the Northern Hemisphere during quiet conditions and small IMF B y component.…”

The Scientific Foundations of Forecasting Magnetospheric Space Weather

“…The utility of these simulations is therefore multi-faceted. Firstly, they enable exploration of the basic physics that controls magnetospheric dynamics; here we mention a few illustrative examples: the analysis of Palmroth et al (2006) using the GUMICS code elucidated the fact that mass transport across the magnetopause may be enhanced for northward IMF; investigating the magnetospheric drivers and energy input under different IMF conditions (Raeder et al 2001;Palmroth et al 2003;Pulkkinen et al 2007;Sergeev et al 2008;Yu and Ridley 2009); exploring the temperature asymmetry in the magnetosheath under different solar wind conditions (Dimmock et al 2015); modelling the effects of shocks on the magnetosphere (Andréeová et al 2008;Oliveira and Raeder 2014); and performing large scale statistical studies (Juusola et al 2014;Facskó et al 2016).…”