Articles | Volume 35, issue 4
Ann. Geophys., 35, 907–922, 2017
Ann. Geophys., 35, 907–922, 2017

Regular paper 01 Aug 2017

Regular paper | 01 Aug 2017

The impact on global magnetohydrodynamic simulations from varying initialisation methods: results from GUMICS-4

Antti Lakka1, Tuija I. Pulkkinen1, Andrew P. Dimmock1, Adnane Osmane1, Ilja Honkonen2, Minna Palmroth3, and Pekka Janhunen2 Antti Lakka et al.
  • 1Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland
  • 2Finnish Meteorological Institute, Helsinki, Finland
  • 3Department of Physics, University of Helsinki, Helsinki, Finland

Abstract. We investigate the effects of different initialisation methods of the GUMICS-4 global magnetohydrodynamic (MHD) simulation to the dynamics in different parts of the Earth's magnetosphere and hence compare five 12 h simulation runs that were initiated by 3 h of synthetic data and followed by 9 h of solar wind measurements using the OMNI data as input. As a reference, we use a simulation run that includes nearly 60 h of OMNI data as input prior to the 9 h interval examined with different initialisations. The selected interval is a high-speed stream event during a 10-day interval (12–22 June 2007). The synthetic initialisations include stepwise, linear and sinusoidal functions of the interplanetary magnetic field with constant density and velocity values. The results show that the solutions converge within 1 h to give a good agreement in both the bow shock and the magnetopause position. However, the different initialisation methods lead to local differences which should be taken into consideration when comparing model results to satellite measurements.

Short summary
We studied the impact on global MHD simulations from different simulation initialisation methods. While the global MHD code used is GUMICS-4 we conclude that the results might be generalisable to other codes as well. It is found that different initialisation methods affect the dynamics of the Earth's space environment by creating differences in momentum transport several hours afterwards. These differences may even grow as a response to rapid solar wind condition changes.